One document matched: draft-ietf-hybi-thewebsocketprotocol-17.xml
<?xml version='1.0' encoding="UTF-8" ?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<?rfc notedraftinprogress='yes'?>
<?rfc rfcprocack="yes"?>
<?rfc toc="yes"?>
<rfc ipr='trust200902' docName='draft-ietf-hybi-thewebsocketprotocol-17' category='std'>
<front>
<title>The WebSocket protocol</title>
<author initials='I.F.' surname='Fette' fullname='Ian Fette'>
<organization>Google, Inc.</organization>
<address>
<email>ifette+ietf@google.com</email>
<uri>http://www.ianfette.com/</uri>
</address>
</author>
<author initials="A." surname="Melnikov" fullname="Alexey Melnikov">
<organization>Isode Ltd</organization>
<address>
<postal>
<street>5 Castle Business Village</street>
<street>36 Station Road</street>
<city>Hampton</city>
<region>Middlesex</region>
<code>TW12 2BX</code>
<country>UK</country>
</postal>
<email>Alexey.Melnikov@isode.com</email>
</address>
</author>
<date month="September" year="2011"/>
<area>Applications</area>
<workgroup>HyBi Working Group</workgroup>
<keyword>HYBI</keyword>
<keyword>websocket</keyword>
<abstract>
<t>The WebSocket protocol enables two-way communication between a client
running untrusted code running in a controlled environment to a remote host
that has opted-in to communications from that code. The security model used
for this is the Origin-based security model commonly used by Web browsers.
The protocol consists of an opening handshake followed by basic message framing,
layered over TCP. The goal of this technology is to provide a mechanism for
browser-based applications that need two-way communication with servers that
does not rely on opening multiple HTTP connections (e.g. using XMLHttpRequest
or <iframe>s and long polling).
</t>
<t>Please send feedback to the hybi@ietf.org mailing list.</t>
</abstract>
</front>
<middle>
<section title='Introduction'>
<section title='Background'>
<t>
<spanx style='emph'>This section is non-normative.</spanx>
</t>
<t>Historically, creating Web applications that need bidirectional
communication between a client and a server (e.g., instant messaging
and gaming applications) has required an abuse of HTTP to
poll the server for updates while sending upstream
notifications as distinct HTTP calls.<xref target="RFC6202" /></t>
<t>This results in a variety of problems:
<list style='symbols'>
<t>The server is forced to use a number of different underlying TCP connections for each client: one for sending information to the client, and a new one for each incoming message.</t>
<t>The wire protocol has a high overhead, with each client-to-server message having an HTTP header.</t>
<t>The client-side script is forced to maintain a mapping from the outgoing connections to the incoming connection to track replies.</t>
</list>
</t>
<!--
////Insert the following text from the Abstract somewhere?
(In theory, any transport protocol could be used so long as it provides for reliable transport, is byte clean, and supports relatively large message sizes. However, for this document, we consider only TCP.)
-->
<t>
A simpler solution would be to use a single TCP connection for traffic in both directions. This is what the WebSocket protocol provides. Combined with the WebSocket API, it provides an alternative to HTTP polling for two-way communication from a Web page to a remote server. <xref target='WSAPI'/>
</t>
<t>The same technique can be used for a variety of Web applications: games, stock tickers, multiuser applications with simultaneous editing, user interfaces exposing server-side services in real time, etc.</t>
<t>
The WebSocket protocol is designed to supersede existing
bidirectional communication technologies which use HTTP as a
transport layer to benefit from existing infrastructure
(proxies, filtering, authentication). Such technologies
were implemented as trade-offs between efficiency and reliability
because HTTP was not initially meant to be used for bidirectional
communication (see <xref target="RFC6202"/> for further discussion). The
WebSocket protocol attempts to address the goals of existing
bidirectional HTTP technologies in the context of the existing
HTTP infrastructure; as such, it is designed to work over HTTP
ports 80 and 443 as well as to support HTTP proxies and
intermediaries, even if this implies some complexity specific to
the current environment. However, the design does not limit
WebSocket to HTTP, and future implementations could use a
simpler handshake over a dedicated port without revinventing
the entire protocol. This last point is important because the
traffic patterns of interactive messaging do not closely match
standard HTTP traffic and can induce unusual loads on some
components.
</t>
</section>
<section title='Protocol Overview'>
<t>
<spanx style='emph'>This section is non-normative.</spanx>
</t>
<t>The protocol has two parts: a handshake, and then the data transfer.</t>
<t>
The handshake from the client looks as follows:</t>
<figure>
<artwork>
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Origin: http://example.com
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13
</artwork>
</figure>
<t>The handshake from the server looks as follows:</t>
<figure>
<artwork>
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
Sec-WebSocket-Protocol: chat
</artwork>
</figure>
<t>The leading line from the client follows the Request-Line format. The leading line from the server follows the Status-Line format. The Request-Line and Status-Line productions are defined in <xref target='RFC2616'/>.
</t>
<t>
After the leading line in both cases come an unordered set of header fields. The meaning of these header fields is specified in <xref target='handshake' /> of this document. Additional header fields may also be present, such as cookies <xref target='RFC6265'/>. The format and parsing of headers is as defined in <xref target='RFC2616'/>.
</t>
<t><vspace blankLines='1'/></t>
<t>Once the client and server have both sent their handshakes, and if the handshake was successful, then the data transfer part starts. This is a two-way communication channel where each side can, independently from the other, send data at will.</t>
<!--Commented out text, as it seems to be misleading:
A message is a complete unit of data at an application level, with the expectation
that many or most applications implementing this protocol (such as web user agents)
provide APIs in terms of sending and receiving messages.
-->
<t>Clients and servers, after a successful handshake, transfer data back and forth
in conceptual units referred to in this specification as "messages".
On the wire a message is composed of one or more frames.
The WebSocket message does not necessarily correspond to a particular network layer
framing, as a fragmented message may be coalesced or split by an intermediary.</t>
<t>A frame has an associated type. Each frame belonging to the same message
contain the same type of data. Broadly speaking, there are types for
textual data, which is interpreted as UTF-8 <xref target='RFC3629'/> text,
binary data (whose interpretation is left up to the application), and control frames,
which are not intended to carry data for the application, but instead for protocol-level
signaling, such as to signal that the connection should be closed. This version of
the protocol defines six frame types and leaves ten reserved for future use.</t>
<!--This looks controversial/misleading to some people:
<t>The WebSocket protocol uses this framing so that specifications that use
the WebSocket protocol can expose such connections using an event-based mechanism
instead of requiring users of those specifications to implement buffering
and piecing together of messages manually.</t>
-->
</section>
<section title='Opening Handshake'>
<t>
<spanx style='emph'>This section is non-normative.</spanx>
</t>
<t>The opening handshake is intended to be compatible with HTTP-based server-side software and intermediaries, so that a single port can be used by both HTTP clients talking to that server and WebSocket clients talking to that server. To this end, the WebSocket client's handshake is an HTTP Upgrade
request:</t>
<figure>
<artwork>
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Origin: http://example.com
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13
</artwork>
</figure>
<t>In compliance with <xref target='RFC2616'/>, header fields in the handshake may be sent by
the client in any order, so the order in which different header fields
are received is not significant.</t>
<t>The "Request-URI" of the GET method <xref target='RFC2616'/> is used to
identify the endpoint of the WebSocket connection, both to allow multiple domains to
be served from one IP address and to allow multiple WebSocket endpoints to be served
by a single server.<vspace blankLines='1'/></t>
<t>The client includes the hostname in the Host header field of its handshake
as per <xref target='RFC2616'/>, so that both the client and the server can verify
that they agree on which host is in use.</t>
<t>Additional header fields are used to select options in the WebSocket protocol.
Typical options available in this version are the subprotocol selector
(|Sec-WebSocket-Protocol|), list of extensions support by the client
(|Sec-WebSocket-Extensions|), |Origin| header field, etc.
The |Sec-WebSocket-Protocol| request-header field can be used to indicate what
subprotocols (application-level protocols layered over the WebSocket protocol) are
acceptable to the client. The server selects one or none of the acceptable protocols
and echoes that value in its handshake to indicate that it has selected that protocol.</t>
<figure>
<artwork> Sec-WebSocket-Protocol: chat</artwork>
</figure>
<t>The |Origin| header field <xref target='I-D.ietf-websec-origin'/> is used to protect
against unauthorized cross-origin use of a WebSocket server by scripts using
the |WebSocket| API in a Web browser. The server is informed of the script origin
generating the WebSocket connection request. If the server does not wish to accept
connections from this origin, it can choose to reject the connection by sending
an appropriate HTTP error code. This header field is sent by browser clients,
for non-browser clients this header field may be sent if it makes sense in the context
of those clients.</t>
<t>Finally, the server has to prove to the client that it received the client's WebSocket handshake, so that the server doesn't accept connections that are not WebSocket connections. This prevents an attacker from tricking a WebSocket server by sending it carefully-crafted packets using |XMLHttpRequest| <xref target="XMLHttpRequest"/> or a |form| submission.</t>
<t>To prove that the handshake was received, the server has to take two pieces of information and combine them to form a response. The first piece of information comes from the |Sec-WebSocket-Key| header field in the client handshake:</t>
<figure>
<artwork>
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
</artwork>
</figure>
<t>
For this header field, the server has to take the value (as present in the header field, e.g. the base64-encoded <xref target='RFC4648'/> version minus any leading and trailing whitespace), and concatenate this with the Globally Unique Identifier (GUID, <xref target='RFC4122'/>) "258EAFA5-E914-47DA-95CA-C5AB0DC85B11" in string form, which is unlikely to be used by network endpoints that do not understand the WebSocket protocol. A SHA-1 hash (160 bits), base64-encoded (see Section 4 of <xref target='RFC4648'/>), of this concatenation is then returned in the server's handshake <xref target='FIPS.180-2.2002' />.
</t>
<t>Concretely, if as in the example above, |Sec-WebSocket-Key| header field had the value "dGhlIHNhbXBsZSBub25jZQ==", the server would concatenate the string "258EAFA5-E914-47DA-95CA-C5AB0DC85B11" to form the string "dGhlIHNhbXBsZSBub25jZQ==258EAFA5-E914-47DA-95CA-C5AB0DC85B11". The server would then take the SHA-1 hash of this, giving the value 0xb3 0x7a 0x4f 0x2c 0xc0 0x62 0x4f 0x16 0x90 0xf6 0x46 0x06 0xcf 0x38 0x59 0x45 0xb2 0xbe 0xc4 0xea. This value is then base64-encoded (see Section 4 of <xref target='RFC4648'/>), to give the value "s3pPLMBiTxaQ9kYGzzhZRbK+xOo=". This value would then be echoed in the |Sec-WebSocket-Accept| header field.</t>
<t>
<vspace blankLines='1'/>
</t>
<t>The handshake from the server is much simpler than the client handshake. The first line is an HTTP Status-Line, with the status code 101:<vspace blankLines='1'/></t>
<figure>
<artwork> HTTP/1.1 101 Switching Protocols</artwork>
</figure>
<t>Any status code other than 101 indicates that the WebSocket handshake
has not completed, and that the semantics of HTTP still apply. The
headers follow the status code.</t>
<t>The |Connection| and |Upgrade| header fields complete the HTTP Upgrade. The |Sec-WebSocket-Accept| header field indicates whether the server is willing to accept the connection. If present, this header field must include a hash of the client's nonce sent in |Sec-WebSocket-Key| along with a predefined GUID. Any other value must not be interpreted as an acceptance of the connection by the server.<vspace blankLines='1'/></t>
<figure>
<artwork>
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
</artwork>
</figure>
<t>These fields are checked by the |WebSocket| client for scripted pages. If the |Sec-WebSocket-Accept| value does not match the expected value, or if the header field is missing, or if the HTTP status code is not 101, the connection will not be established and WebSocket frames will not be sent.</t>
<t>Option fields can also be included. In this version of the protocol, the main option field is |Sec-WebSocket-Protocol|, which indicates the subprotocol that the server has selected. WebSocket clients verify that the server included one of the values as was specified in the WebSocket client's handshake. A server that speaks multiple subprotocols has to make sure it selects one based on the client's handshake and specifies it in its handshake.<vspace blankLines='1'/></t>
<figure>
<artwork> Sec-WebSocket-Protocol: chat</artwork>
</figure>
<t>The server can also set cookie-related option fields to <spanx style='emph'>set</spanx> cookies, as described in <xref target='RFC6265'/>.
</t>
</section>
<section title='Closing Handshake'>
<t>
<spanx style='emph'>This section is non-normative.</spanx>
</t>
<t>The closing handshake is far simpler than the opening handshake.</t>
<t>Either peer can send a control frame with data containing a specified control sequence to begin the closing handshake (detailed in <xref target='closeframe'/>). Upon receiving such a frame, the other peer sends a close frame in response, if it hasn't already sent one. Upon receiving <spanx style='emph'>that</spanx> control frame, the first peer then closes the connection, safe in the knowledge that no further data is forthcoming.</t>
<t>After sending a control frame indicating the connection should be closed, a peer does not send any further data; after receiving a control frame indicating the connection should be closed, a peer discards any further data received.</t>
<t>It is safe for both peers to initiate this handshake simultaneously.</t>
<t>The closing handshake is intended to complement the TCP closing handshake (FIN/ACK), on the basis that the TCP closing handshake is not always reliable end-to-end, especially in the presence of intercepting proxies and other intermediaries.</t>
<t>By sending a close frame and waiting for a close frame in response, certain cases are avoided where data may be unnecessarily lost. For instance, on some platforms, if a socket is closed with data in the receive queue, a RST packet is sent, which will then cause recv() to fail for the party that received the RST, even if there was data waiting to be read.</t>
</section>
<section title='Design Philosophy'>
<t>
<spanx style='emph'>This section is non-normative.</spanx>
</t>
<t>The WebSocket protocol is designed on the principle that there should be minimal framing (the only framing that exists is to make the protocol frame-based instead of stream-based, and to support a distinction between Unicode text and binary frames). It is expected that metadata would be layered on top of WebSocket by the application layer, in the same way that metadata is layered on top of TCP by the application layer (e.g., HTTP).</t>
<t>Conceptually, WebSocket is really just a layer on top of TCP that does the following:
<list style='symbols'>
<t>adds a Web "origin"-based security model for browsers</t>
<!--////Alexey: does this require further editing?-->
<t>adds an addressing and protocol naming mechanism to support
multiple services on one port and multiple host names on one IP
address;</t>
<t>layers a framing mechanism on top of TCP to get back to the IP
packet mechanism that TCP is built on, but without length limits</t>
<t>includes an additional closing handshake in-band that is designed
to work in the presence of proxies and other intermediaries</t>
</list>
Other than that, WebSocket adds nothing. Basically it is intended
to be as close to just exposing raw TCP to script as possible given
the constraints of the Web. It's also designed in such a way that
its servers can share a port with HTTP servers, by having its
handshake be a valid HTTP Upgrade request mechanism also. One could
conceptually use other protocols to establish client-server messaging,
but the intent of WebSockets was to provide a relatively simple
protocol that can coexist with HTTP and deployed HTTP infrastructure
(such as proxies) that is as close to TCP as is safe for use with
such infrastructure given security considerations, with targeted
additions to simplify usage and make simple things simple (such
as the addition of message semantics).</t>
<t>The protocol is intended to be extensible; future versions will likely introduce additional concepts such as multiplexing.</t>
</section>
<section title='Security Model' anchor='secmodel'>
<t>
<spanx style='emph'>This section is non-normative.</spanx>
</t>
<t>The WebSocket protocol uses the origin model used by Web browsers to restrict which Web pages can contact a WebSocket server when the WebSocket protocol is used from a Web page. Naturally, when the WebSocket protocol is used by a dedicated client directly (i.e. not from a Web page through a Web browser), the origin model is not useful, as the client can provide any arbitrary origin string.</t>
<t>This protocol is intended to fail to establish a connection with servers of pre-existing protocols like SMTP <xref target='RFC5321'/> and HTTP, while allowing HTTP servers to opt-in to supporting this protocol if desired. This is achieved by having a strict and elaborate handshake, and by limiting the data that can be inserted into the connection before the handshake is finished (thus limiting how much the server can be influenced).</t>
<t>It is similarly intended to fail to establish a connection when data from other protocols, especially HTTP, is sent to a WebSocket server, for example as might happen if an HTML |form| were submitted to a WebSocket server. This is primarily achieved by requiring that the server prove that it read the handshake, which it can only do if the handshake contains the appropriate parts which themselves can only be sent by a WebSocket handshake. In particular, at the time of writing of this specification, fields starting with |Sec-| cannot be set by an attacker from a Web browser using only HTML and JavaScript APIs such as |XMLHttpRequest| <xref target="XMLHttpRequest"/>.</t>
</section>
<section title='Relationship to TCP and HTTP'>
<t>
<spanx style='emph'>This section is non-normative.</spanx>
</t>
<t>The WebSocket protocol is an independent TCP-based protocol. Its only relationship to HTTP is that its handshake is interpreted by HTTP servers as an Upgrade request.</t>
<t>By default the WebSocket protocol uses port 80 for regular WebSocket connections and port 443 for WebSocket connections tunneled over TLS <xref target='RFC2818'/>.</t>
</section>
<section title='Establishing a Connection'>
<t>
<spanx style='emph'>This section is non-normative.</spanx>
</t>
<t>
When a connection is to be made to a port that is shared by an HTTP
server (a situation that is quite likely to occur with traffic to
ports 80 and 443), the connection will appear to the HTTP server to
be a regular GET request with an Upgrade offer. In relatively simple
setups with just one IP address and a single server for all traffic
to a single hostname, this might allow a practical way for systems
based on the WebSocket protocol to be deployed. In more elaborate
setups (e.g. with load balancers and multiple servers), a dedicated
set of hosts for WebSocket connections separate from the HTTP servers
is probably easier to manage. At the time of writing of this
specification, it should be noted that connections on port 80 and 443
have significantly different success rates, with connections on
port 443 being significantly more likely to succeed, though this may
change with time.
</t>
</section>
<section title='Subprotocols Using the WebSocket protocol'>
<t>
<spanx style='emph'>This section is non-normative.</spanx>
</t>
<t>The client can request that the server use a specific subprotocol by including the |Sec-WebSocket-Protocol| field in its handshake. If it is specified, the server needs to include the same field and one of the selected subprotocol values in its response for the connection to be established.</t>
<t>These subprotocol names should be registered as per <xref target='spr'/>. To avoid potential collisions, it is recommended to use names that contain the ASCII version of the domain name of the subprotocol's originator. For example, if Example Corporation were to create a Chat subprotocol to be implemented by many servers around the Web, they could name it "chat.example.com". If the Example Organization called their competing subprotocol "chat.example.org", then the two subprotocols could be implemented by servers simultaneously, with the server dynamically selecting which subprotocol to use based on the value sent by the client.</t>
<t>Subprotocols can be versioned in backwards-incompatible ways by changing the subprotocol name, e.g. going from "bookings.example.net" to "v2.bookings.example.net". These subprotocols would be considered completely separate by WebSocket clients. Backwards-compatible versioning can be implemented by reusing the same subprotocol string but carefully designing the actual subprotocol to support this kind of extensibility.</t>
</section>
</section>
<section title='Conformance Requirements'>
<t>All diagrams, examples, and notes in this specification are non-normative, as are all sections explicitly marked non-normative. Everything else in this specification is normative.</t>
<t>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119. <xref target='RFC2119'/>
</t>
<t>Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or "return false and abort these steps") are to be interpreted with the meaning of the key word ("must", "should", "may", etc) used in introducing the algorithm.</t>
<t>Conformance requirements phrased as algorithms or specific steps MAY be implemented in any manner, so long as the end result is equivalent. (In particular, the algorithms defined in this specification are intended to be easy to follow, and not intended to be performant.)</t>
<section title='Terminology and other conventions'>
<t>
<spanx style='emph'>ASCII</spanx> shall mean the character-encoding scheme defined in <xref target='ANSI.X3-4.1986'/>.
</t>
<t>This document makes reference to UTF-8 values and uses UTF-8
notational formats as defined in STD 63 <xref target='RFC3629'/>.
</t>
<t>Key Terms such as named algorithms or
definitions are indicated like <spanx style='emph'>this</spanx>.
</t>
<t>Names of header fields or variables are indicated like |this|.
</t>
<t>Variable values are indicated like /this/.
</t>
<t>This document references the procedure to
<spanx style='emph'>Fail the WebSocket Connection</spanx>. This procedure is
defined in <xref target='fail_ws'/>.
</t>
<t>
<spanx style='emph'>Converting a string to ASCII lowercase</spanx> means replacing all characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) with the corresponding characters in the range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z).
</t>
<t>
Comparing two strings in an <spanx style='emph'>ASCII case-insensitive</spanx> manner means comparing them exactly, code point for code point, except that the characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) and the corresponding characters in the range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) are considered to also match.
</t>
<t>
The term "URI" is used in this document as defined in <xref target='RFC3986'/>.
</t>
<t>
When an implementation is required to <spanx style='emph'>send</spanx> data as part of the WebSocket protocol, the implementation MAY delay the actual transmission arbitrarily, e.g. buffering data so as to send fewer IP packets.
</t>
<t>Note that this document uses both <xref target='RFC5234'/> and
<xref target='RFC2616'/> variants of ABNF in different sections.</t>
</section>
</section>
<section title='WebSocket URIs' anchor='ws_uris'>
<t>This specification defines two URI schemes, using the ABNF syntax
defined in RFC 5234 <xref target='RFC5234'/>, and terminology and ABNF
productions defined by the URI specification RFC 3986 <xref
target='RFC3986'/>.
</t>
<t>
<figure height="" suppress-title="false" width="" alt="" title="" align="left">
<artwork type="abnf" height="" name="" width="" alt="" align="left" xml:space="preserve"><![CDATA[
ws-URI = "ws:" "//" host [ ":" port ] path [ "?" query ]
wss-URI = "wss:" "//" host [ ":" port ] path [ "?" query ]
host = <host, defined in [RFC3986], Section 3.2.2>
port = <port, defined in [RFC3986], Section 3.2.3>
path = <path-abempty, defined in [RFC3986], Section 3.3>
query = <query, defined in [RFC3986], Section 3.4>
]]></artwork></figure>
</t>
<t>
The port component is OPTIONAL; the default for "ws" is port
80, while the default for "wss" is port 443.
</t>
<t>
The URI is called "secure" (and it said that "the secure flag is
set") if the scheme component matches "wss" case-insensitively.
</t>
<t>
The "resource-name" (also known as /resource name/ in <xref target='clienths'/>)
can be constructed by concatenating
<list style="symbols">
<t>
"/" if the path component is empty
</t>
<t>
the path component
</t>
<t>
"?" if the query component is non-empty
</t>
<t>
the query component
</t>
</list>
</t>
<t>
Fragment identifiers are meaningless in the context of WebSocket URIs,
and MUST NOT be used on these URIs. The character "#" in
URIs MUST be escaped as %23 if used as part of the query component.
</t>
</section>
<section title='Opening Handshake' anchor='handshake'>
<section title='Client Requirements' anchor='clienths'>
<t>To <spanx style='emph'>Establish a WebSocket Connection</spanx>, a
client opens a connection and sends a handshake as defined in this
section. A connection is defined to initially be in a CONNECTING state.
A client will need to supply a /host/, /port/, /resource name/,
and a /secure/ flag, which are the components of a WebSocket URI as
discussed in <xref target='ws_uris'/>, along with a list of /protocols/
and /extensions/ to be used. Additionally, if the client is a web
browser, it supplies /origin/.
</t>
<t>Clients running in controlled environments, e.g. browsers on
mobile handsets tied to specific carriers, MAY offload the management
of the connection to another agent on the network. In such a
situation, the client for the purposes of this specification is
considered to include both the handset software and any such
agents.</t>
<t>When the client is to <spanx style='emph'>Establish a
WebSocket Connection</spanx> given a set
of (/host/, /port/, /resource name/, and /secure/ flag), along with a
list of /protocols/ and /extensions/ to be used, and an /origin/ in the
case of web browsers,
it MUST open a connection, send an opening handshake, and read the
server's handshake in response. The exact requirements of how the
connection should be opened, what should be sent in the opening
handshake, and how the server's response should be interpreted, are
as follows in this section.
In the following text, we will use terms
from <xref target='ws_uris'/> such as "/host/" and
"/secure/ flag" as defined in that section.
<list style='numbers'>
<t>The components of the WebSocket URI passed into this algorithm
(/host/, /port/, /resource name/ and /secure/ flag) MUST be valid
according to the specification of WebSocket URIs specified in <xref
target='ws_uris'/>. If any of the components are invalid, the
client MUST <spanx style='emph'>Fail the WebSocket
Connection</spanx> and abort these steps.
</t>
<t>If the client already has a WebSocket connection to the
remote host (IP address) identified by /host/ and port /port/ pair,
even if the remote host is known by another name, the client MUST
wait until that connection has
been established or for that connection to have failed. There MUST be
no more than one connection in a CONNECTING state. If
multiple connections to the same IP address are attempted
simultaneously, the client MUST serialize them so that there is
no more than one connection at a time running through the following
steps.
<vspace blankLines='1'/>
If the client cannot determine the IP address of the remote host
(for example because all communication is being done through a proxy
server that performs DNS queries itself), then the client MUST
assume for the purposes of this step that each host name refers to a
distinct remote host, and instead the client SHOULD limit the total number of
simultaneous pending connections to a reasonably
low number (e.g., the client might allow simultaneous pending connections
to a.example.com and b.example.com, but if thirty simultaneous connections
to a single host are requested, that may not be allowed).
For example in a Web browser context, the client needs to consider the number of tabs the user
has open in setting a limit to the number of simultaneous pending connections.
<vspace blankLines='1'/>
NOTE: This makes it harder for a script to perform a denial of
service attack by just opening a large number of WebSocket
connections to a remote host. A server can further reduce the load
on itself when attacked by pausing before
closing the connection, as that will reduce the rate at which the
client reconnects.
<vspace blankLines='1'/>
NOTE: There is no limit to the number of established WebSocket
connections a client can have with a single remote host.
Servers can refuse to accept connections from hosts/IP addresses with an
excessive number of existing connections, or disconnect
resource-hogging connections when suffering high load.</t>
<t><spanx style='emph'>Proxy Usage</spanx>: If the client is
configured to use a proxy when using the WebSocket protocol to
connect to host /host/ and port /port/, then the client
SHOULD connect to that proxy and ask it to open a TCP connection to
the host given by /host/ and the port given by /port/.
<list style='empty'>
<t>EXAMPLE: For example, if the client uses an HTTP proxy for
all traffic, then if it was to try to connect to port 80 on server
example.com, it might send the following lines to the proxy
server:
<vspace blankLines='1'/>
<figure>
<artwork>
CONNECT example.com:80 HTTP/1.1
Host: example.com
</artwork>
</figure>
</t>
<t>If there was a password, the connection might look like:
<vspace blankLines='1'/>
<figure>
<artwork>
CONNECT example.com:80 HTTP/1.1
Host: example.com
Proxy-authorization: Basic ZWRuYW1vZGU6bm9jYXBlcyE=
</artwork>
</figure>
</t>
</list>
If the client is not configured to use a proxy, then a
direct TCP connection SHOULD be opened to the host given by
/host/ and the port given by /port/.
<vspace blankLines='1'/>
NOTE: Implementations that do not expose explicit UI for selecting a
proxy for WebSocket connections separate from other proxies are
encouraged to use a SOCKS5 <xref target='RFC1928'/> proxy for WebSocket connections, if
available, or failing that, to prefer the proxy configured for HTTPS
connections over the proxy configured for HTTP connections.
<vspace blankLines='1'/>
For the purpose of proxy autoconfiguration scripts, the URI to pass
the function MUST be constructed from /host/, /port/, /resource
name/, and the /secure/ flag using the definition of a
WebSocket URI as given in <xref target="ws_uris" />.
<vspace blankLines='1'/>
NOTE: The WebSocket protocol can be identified in proxy
autoconfiguration scripts from the scheme ("ws" for
unencrypted connections and "wss" for encrypted
connections).</t>
<t>If the connection could not be opened, either because a direct
connection failed or because any proxy used returned an error, then
the client MUST <spanx style='emph'>Fail the WebSocket
Connection</spanx> and abort the connection attempt.</t>
<t> If /secure/ is true, the client MUST perform a TLS handshake
over the connection after opening the connection and before
sending the handshake data
<xref target='RFC2818'/>. If this fails (e.g. the server's
certificate could not be verified), then the client MUST <spanx
style='emph'>Fail the WebSocket Connection</spanx>
and abort the connection. Otherwise, all
further communication on this channel MUST run through the encrypted
tunnel. <xref target='RFC5246'/>
<vspace blankLines='1'/>
Clients MUST use the Server Name Indication extension in the TLS
handshake. <xref target='RFC6066'/>
</t>
</list>
</t>
<t anchor='clientopenhs'>Once a connection to the server has been
established (including a
connection via a proxy or over a TLS-encrypted tunnel), the client
MUST send an opening handshake to the server. The handshake consists of
an HTTP upgrade request, along with a list of required and optional
header fields. The requirements for this handshake are as follows.
<list style='numbers'>
<t>The handshake MUST be a valid HTTP request as specified by <xref
target='RFC2616'/>.</t>
<t>The Method of the request MUST be GET and the HTTP version MUST be
at least 1.1.
<vspace blankLines='1' />
For example, if the WebSocket URI is
"ws://example.com/chat", The first line sent should be
"GET /chat HTTP/1.1"</t>
<t>The "Request-URI" part of the request MUST match the /resource name/
<xref target='ws_uris'/> (a relative URI), or be an absolute http/https URI that,
when parsed, has a /resource name/, /host/ and /port/ that match the corresponding
<!--////Add an example for clarity?-->
ws/wss URI.</t>
<t>The request MUST contain a "Host" header field whose value is
equal to /host/.</t>
<t>The request MUST contain an "Upgrade" header field whose value
is equal to "websocket".</t>
<t>The request MUST contain a "Connection" header field whose
value MUST include the "Upgrade" token.</t>
<t>The request MUST include a header field with the name
"Sec-WebSocket-Key". The value of this header field MUST be a
nonce consisting of a randomly selected 16-byte value that has been
base64-encoded (see Section 4 of <xref target='RFC4648'/>). The nonce MUST be
selected randomly for each connection. <vspace blankLines='1'/>
NOTE: As an example, if the randomly selected value was the sequence
of bytes 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0a 0x0b 0x0c
0x0d 0x0e 0x0f 0x10, the value of the header field would be
"AQIDBAUGBwgJCgsMDQ4PEC=="</t>
<t>The request MUST include a header field with the name
"Origin" <xref target='I-D.ietf-websec-origin'/> if the request is coming from a
browser client. If the connection is from a non-browser client, the
request MAY include this header field if the semantics of that client match
the use-case described here for browser clients.
The value of this header field is
the ASCII serialization of origin of the context in which the code
establishing the connection is running. See <xref target='I-D.ietf-websec-origin'/>
for the details of how this header field value is constructed.
<vspace blankLines='1'/>
As an example, if code downloaded from www.example.com attempts to
establish a connection to ww2.example.com, the value of the header field
would be "http://www.example.com".</t>
<t>The request MUST include a header field with the name
"Sec-WebSocket-Version". The value of this header field MUST be 13.
<!--////Alexey: we need to update that for -09/-10/-11, etc. -->
<spanx style='emph'>Note: Although drafts -09, -10, -11 and -12 were published, as they
were mostly comprised of editorial changes and clarifications and not changes
to the wire protocol, values 9, 10, 11 and 12 were not used as valid values for
Sec-WebSocket-Version. These values were reserved in the IANA registry
but were not and will not be used.</spanx>
</t>
<t anchor="swp-defined">The request MAY include a header field with the name
"Sec-WebSocket-Protocol". If present, this value indicates
one or more comma separated subprotocol the client wishes to speak, ordered by preference.
The elements that
comprise this value MUST be non-empty strings with characters in
the range U+0021 to U+007E not including separator characters as
defined in <xref target='RFC2616'/>, and MUST all be unique strings.
The ABNF for the value of this header field is 1#token, where the
definitions of constructs and rules are as given in <xref target='RFC2616'/>.</t>
<t>The request MAY include a header field with the name
"Sec-WebSocket-Extensions". If present, this value
indicates the protocol-level extension(s) the client wishes to
speak. The interpretation and format of
this header field is described in <xref target="negotiation" />.</t>
<t> The request MAY include any other header fields, for example cookies
<xref target='RFC6265'/> and/or authentication related header fields
such as Authorization header field <xref target='RFC2616'/>, which are
processed according to documents that define them.
</t>
</list>
</t>
<t>Once the client's opening handshake has been sent, the client MUST
wait for a response from the server before sending any further data.
The client MUST validate the server's response as follows:
<list style='numbers'>
<t>If the status code received from the server is not 101, the
client handles the response per HTTP <xref target='RFC2616'/> procedures,
in particular the client might perform authentication if it receives
401 status code, the server might redirect the client using a 3xx status code
(but clients are not required to follow them), etc.
Otherwise, proceed as follows.</t>
<t>If the response lacks an "Upgrade" header field or the
"Upgrade" header field contains a value that is not an ASCII
case-insensitive match for the value "websocket", the
client MUST <spanx style='emph'>Fail the WebSocket Connection
</spanx>.</t>
<t>If the response lacks a "Connection" header field or the
"Connection" header field doesn't contain a token that is an ASCII
case-insensitive match for the value "Upgrade", the client
MUST <spanx style='emph'>Fail the WebSocket Connection</spanx>.</t>
<t>If the response lacks a "Sec-WebSocket-Accept" header field or
the "Sec-WebSocket-Accept" contains a value other than the
base64-encoded SHA-1 of the concatenation of the
"Sec-WebSocket-Key" (as a string, not base64-decoded) with
the string "258EAFA5-E914-47DA-95CA-C5AB0DC85B11", but ignoring
any leading and trailing whitespace, the
client MUST <spanx style='emph'>Fail the WebSocket Connection</spanx>
</t>
<t>If the response includes a "Sec-WebSocket-Extensions"
header field, and this header field indicates the use of an extension that was
not present in the client' handshake (the server has indicated
an extension not requested by the client), the client MUST <spanx
style='emph'>Fail the WebSocket Connection</spanx>.
(The parsing of this header field to determine which
extensions are requested is discussed in <xref
target='negotiation'/>.)</t>
<t>If the response includes a "Sec-WebSocket-Protocol"
header field, and this header field indicates the use of a subprotocol that was
not present in the client' handshake (the server has indicated
a subprotocol not requested by the client), the client MUST <spanx
style='emph'>Fail the WebSocket Connection</spanx>.</t>
</list>
</t>
<t>If the server's response does not conform to the requirements
for the server's handshake as defined in this section and in
<xref target='server_handshake'/>, the client MUST <spanx
style='emph'>Fail the WebSocket Connection</spanx>.
</t>
<t>Please note that according to <xref target='RFC2616'/> all header field
names in both HTTP requests and HTTP responses are case-insensitive.</t>
<t> If the server's response is validated as provided for above, it
is said that <spanx style='emph'>The WebSocket Connection is
Established</spanx> and that the WebSocket Connection is in the OPEN
state. The <spanx style='emph'>Extensions In Use</spanx>
is defined to be a (possibly empty) string, the value of
which is equal to the value of the |Sec-WebSocket-Extensions| header field
supplied by the server's handshake, or the null value if that
header field was not present in the server's handshake. The <spanx
style='emph'>Subprotocol In Use</spanx> is defined to be the value of
the |Sec-WebSocket-Protocol| header field in the server's handshake, or
the null value if that header field was not present in the server's
handshake. Additionally, if any header fields in the server's handshake
indicate that cookies should be set (as defined by <xref
target='RFC6265'/>),
<!--////Alexey: Is this text needed, or can this be deleted?-->
these cookies are referred to
as <spanx style='emph'>Cookies Set During the Server's Opening
Handshake</spanx>.
</t>
</section>
<section title='Server-side Requirements'>
<t>Servers MAY offload the management of the connection to other
agents on the network, for example load balancers and reverse proxies.
In such a situation, the server for the purposes of this specification is
considered to include all parts of the server-side infrastructure from
the first device to terminate the TCP connection all the way to the
server that processes requests and sends responses.</t>
<t>EXAMPLE: For example, a data center might have a server that
responds to WebSocket requests with an appropriate handshake, and
then passes the connection to another server to actually process the
data frames. For the purposes of this specification, the "server" is
the combination of both computers.</t>
<section title='Reading the Client's Opening Handshake'>
<t>When a client starts a WebSocket connection, it sends its part of
the opening handshake. The server must parse at least part of this
handshake in order to obtain the necessary information to generate
the server part of the handshake.</t>
<t>The client's opening handshake consists of the following
parts. If the server, while reading the handshake, finds that the
client did not send a handshake that matches the description below
(note that as per <xref target='RFC2616'/> the order of the header
fields is not important),
including but not limited to any violations of the ABNF grammar
specified for the components of the handshake,
the server MUST stop processing the client's handshake, and
return an HTTP response with an appropriate error code (such as 400
Bad Request).
<list style='numbers'>
<t>An HTTP/1.1 or higher GET request, including a
"Request-URI" <xref target='RFC2616'/> that should be
interpreted as a /resource name/ <xref target='ws_uris'/>
(or an absolute HTTP/HTTPS URI containing the /resource name/). </t>
<t>A "Host" header field containing the server's
authority.</t>
<t>An "Upgrade" header field containing the value "websocket",
treated as an ASCII case-insensitive value.</t>
<t>A "Connection" header field that includes the token "Upgrade",
treated as an ASCII case-insensitive value.</t>
<t>A "Sec-WebSocket-Key" header field with a base64-encoded
(see Section 4 of <xref target='RFC4648'/>) value that, when decoded, is 16 bytes in length.</t>
<t>A "Sec-WebSocket-Version" header field, with a value of 13.</t>
<t>Optionally, an "Origin" header field. This
header field is sent by all browser clients. A connection attempt
lacking this header field SHOULD NOT be interpreted as coming from
a browser client.</t>
<t>Optionally, a "Sec-WebSocket-Protocol" header field, with a
list of values indicating which protocols the client would like to
speak, ordered by preference.</t>
<t>Optionally, a "Sec-WebSocket-Extensions" header field, with
a list of values indicating which extensions the client would like
to speak. The interpretation of this header field is discussed in
<xref target="negotiation" />.</t>
<t>Optionally, other header fields, such as those used to send cookies
or request authentication to a server. Unknown header fields are ignored,
as per <xref target="RFC2616"/>.</t>
</list>
</t>
</section>
<section title='Sending the Server's Opening Handshake'
anchor='server_handshake'>
<t>When a client establishes a WebSocket connection to a server, the
server MUST complete the following steps to accept the connection
and send the server's opening handshake.
<list style='numbers'>
<t>If the connection is happening on an HTTPS (HTTP-over-TLS) port,
perform a TLS handshake
over the connection. If this fails (e.g. the client indicated a
host name in the extended client hello "server_name"
extension that the server does not host), then close the
connection; otherwise, all further communication for the
connection (including the server's handshake) MUST run through
the encrypted tunnel. <xref target='RFC5246'/></t>
<t>The server can perform additional client authentication,
for example by returning a 401 status code with the corresponding
WWW-Authenticate header field as described in <xref target='RFC2616'/>.</t>
<t>The server MAY redirect the client using a 3xx status code
<xref target='RFC2616'/>. Note that this step can happen together
with, before or after the optional authentication step described above.</t>
<t anchor='server_handshake_info'>Establish the following information:
<list style='hanging'>
<t hangText='/origin/'><vspace blankLines='0'/>
The |Origin| header field in the client's handshake
indicates the origin of the script establishing the connection.
The origin is serialized to ASCII and converted to lowercase.
The server MAY use this information as part of a determination
of whether to accept the incoming connection. If the server does
not validate the origin, it will accept connections from anywhere.
If the server does not wish to accept this connection, it MUST
return an appropriate HTTP error code (e.g. 403 Forbidden) and
abort the WebSocket handshake described in this section.
For more detail, refer to <xref
target="securityconsiderations" />.</t>
<t hangText='/key/'><vspace blankLines='0'/>
The |Sec-WebSocket-Key| header field in the client's handshake
includes a base64-encoded value that, if decoded, is 16 bytes in
length. This (encoded) value is used in the creation of the
server's handshake to indicate an acceptance of the
connection. It is not necessary for the server to base64-decode
the "Sec-WebSocket-Key" value.</t>
<t hangText='/version/'><vspace blankLines='0'/>
The |Sec-WebSocket-Version| header field in the client's handshake
includes the version of the WebSocket protocol the client is
attempting to communicate with. If this version does not match
a version understood by the server, the server MUST abort the
websocket handshake described in this section and instead send an
appropriate HTTP error code (such as 426 Upgrade Required), and a
|Sec-WebSocket-Version| header field indicating the
version(s) the server is capable of understanding.
</t>
<t hangText='/resource name/'><vspace blankLines='0'/>
An identifier for the service provided by the server. If the
server provides multiple services, then the value should be
derived from the resource name given in the client's
handshake from the Request-URI <xref target='RFC2616'/>
of the GET method. If the requested service is not available, the
server MUST send an appropriate HTTP error code (such as 404 Not
Found) and abort the WebSocket handshake.</t>
<t hangText='/subprotocol/'><vspace blankLines='0'/>
Either a single value representing the subprotocol the
server is ready to use or null. The value chosen MUST be derived from the
client's handshake, specifically by selecting one of the
values from the "Sec-WebSocket-Protocol" field that the
server is willing to use for this connection (if any). If the
client's handshake did not contain such a header field, or if the
server does not agree to any of the client's requested
subprotocols, the only acceptable value is null. The
absence of such a field is equivalent to the null value (meaning
that if the server does not wish to agree to one of the suggested
subprotocols, it MUST NOT send back a |Sec-WebSocket-Protocol|
header field in its response). The empty
string is not the same as the null value for these purposes, and
is not a legal value for this field. The ABNF for the
value of this header field is (token), where the
definitions of constructs and rules are as given in <xref
target='RFC2616' />.</t>
<t hangText='/extensions/'><vspace blankLines='0'/>
A (possibly empty) list representing the protocol-level
extensions the server is ready to use. If the server supports
multiple extensions, then the value MUST be derived from the
client's handshake, specifically by selecting one or more of
the
values from the "Sec-WebSocket-Extensions" field. The
absence of such a field is equivalent to the null value. The
empty string is not the same as the null value for these
purposes. Extensions not listed by the client MUST NOT be listed.
The method by which these values should be selected and
interpreted is discussed in <xref target="negotiation" />.</t>
</list>
</t>
<t>If the server chooses to accept the incoming connection, it
MUST reply with a valid HTTP response indicating the following.
<list style='numbers'>
<t>A Status-Line with a 101 response code as per RFC 2616
<xref target='RFC2616'/>. Such a response could look like
"HTTP/1.1 101 Switching Protocols"</t>
<t>An "Upgrade" header field with value
"websocket" as per RFC 2616 <xref target='RFC2616'/>.
</t>
<t>A "Connection" header field with value
"Upgrade"</t>
<t>A "Sec-WebSocket-Accept" header field. The value of this
header field is constructed by concatenating /key/, defined above
in <xref target='server_handshake_info' /> of
<xref target='server_handshake' />, with the string
"258EAFA5-E914-47DA-95CA-C5AB0DC85B11", taking the
SHA-1 hash of this concatenated value to obtain a 20-byte value,
and base64-encoding (see Section 4 of <xref target='RFC4648'/>) this 20-byte hash.
<vspace blankLines='1'/>The ABNF <xref target='RFC2616'/> of this header field is defined as
follows:
<figure>
<artwork>
Sec-WebSocket-Accept = base64-value-non-empty
base64-value-non-empty = (1*base64-data [ base64-padding ]) |
base64-padding
base64-data = 4base64-character
base64-padding = (2base64-character "==") |
(3base64-character "=")
base64-character = ALPHA | DIGIT | "+" | "/"
</artwork>
</figure>
<vspace blankLines='1'/>
NOTE: As an example, if the value of the
"Sec-WebSocket-Key" header field in the client's handshake
were "dGhlIHNhbXBsZSBub25jZQ==", the server would
append the string
"258EAFA5-E914-47DA-95CA-C5AB0DC85B11" to form the
string
"dGhlIHNhbXBsZSBub25jZQ==258EAFA5-E914-47DA-95CA-C5AB0DC85B11".
The server would then take the SHA-1 hash of this string, giving
the value 0xb3 0x7a 0x4f 0x2c 0xc0 0x62 0x4f 0x16 0x90 0xf6 0x46
0x06 0xcf 0x38 0x59 0x45 0xb2 0xbe 0xc4 0xea. This value is then
base64-encoded, to give the value
"s3pPLMBiTxaQ9kYGzzhZRbK+xOo=", which would be
returned in the "Sec-WebSocket-Accept" header field.</t>
<t>Optionally, a "Sec-WebSocket-Protocol" header field,
with a value /subprotocol/ as defined in
<xref target='server_handshake_info' />
of <xref target='server_handshake' />.</t>
<t>Optionally, a "Sec-WebSocket-Extensions" header field,
with a value /extensions/ as defined in
<xref target='server_handshake_info' />
of <xref target='server_handshake' />. If multiple extensions are
to be used, they can all be listed in a single
Sec-WebSocket-Extensions header field, or split between multiple instances
of the Sec-WebSocket-Extensions header field.
</t>
</list>
</t>
</list>
</t>
<t>This completes the server's handshake. If the server
finishes these steps without aborting the WebSocket handshake,
the server considers the WebSocket connection to be established and
that the WebSocket connection is in the OPEN state. At this point, the
server may begin sending (and receiving) data.
<!--
and
if the client does not then fail the WebSocket connection, then the
connection is established and the server may begin sending and
receiving data.-->
</t>
</section>
</section>
<section title='Collected ABNF for new header fields used in handshake'>
<t>This section is using ABNF syntax/rules from Section 2.1 of
<xref target="RFC2616"/>, including "implied *LWS rule".
</t>
<t>Note that the following ABNF conventions are used in this section:
Some names of the rules correspond to names of the corresponding header fields.
Such rules express values of the corresponding header fields, for example
the Sec-WebSocket-Key ABNF rule describes syntax of the Sec-WebSocket-Key
header field value.
ABNF rules with the "-Client" suffix in the name are only used in requests sent
by the client to the server; ABNF rules with the "-Server" suffix in the name
are only used in responses sent by the server to the client. For example,
the ABNF rule Sec-WebSocket-Protocol-Client describes syntax of the
Sec-WebSocket-Protocol header field value sent by the client to the server.
</t>
<t>The following new header field can be sent during the handshake from the client
to the server:</t>
<figure>
<artwork>
Sec-WebSocket-Key = base64-value-non-empty
Sec-WebSocket-Extensions = extension-list
Sec-WebSocket-Protocol-Client = 1#token
Sec-WebSocket-Version-Client = version
base64-value-non-empty = (1*base64-data [ base64-padding ]) |
base64-padding
base64-data = 4base64-character
base64-padding = (2base64-character "==") |
(3base64-character "=")
base64-character = ALPHA | DIGIT | "+" | "/"
extension-list = 1#extension
extension = extension-token *( ";" extension-param )
extension-token = registered-token
registered-token = token
extension-param = token [ "=" (token | quoted-string) ]
;When using the quoted-string syntax variant, the value
;after quoted-string unescaping MUST conform to the 'token' ABNF.
NZDIGIT = "1" | "2" | "3" | "4" | "5" | "6" |
"7" | "8" | "9"
version = DIGIT | (NZDIGIT DIGIT) |
("1" DIGIT DIGIT) | ("2" DIGIT DIGIT)
; Limited to 0-255 range, with no leading zeros
</artwork>
</figure>
<t>
The following new header field can be sent during the handshake from the server
to the client:
</t>
<figure>
<artwork>
Sec-WebSocket-Extensions = extension-list
Sec-WebSocket-Accept = base64-value-non-empty
Sec-WebSocket-Protocol-Server = token
Sec-WebSocket-Version-Server = 1#version
</artwork>
</figure>
</section>
<section title='Supporting multiple versions of WebSocket protocol'>
<t>This section provides some guidance on supporting multiple versions
of the WebSocket protocol in clients and servers.</t>
<t>Using the WebSocket version advertisement capability
(the "Sec-WebSocket-Version" header field) client can initially request
the version of the WebSocket protocol that it prefers (which doesn't
necessarily have to be the latest supported by the client).
If the server supports the requested version and the handshake message
is otherwise valid, the server will accept that version.
If the server doesn't support the requested version, it MUST respond
with a Sec-WebSocket-Version header field (or multiple Sec-WebSocket-Version
header fields) containing all versions it is willing to use.
At this point, if the client supports one of the advertised versions,
it can repeat the WebSocket handshake using a new version value.</t>
<t>The following example demonstrates version negotiation described above:</t>
<figure>
<artwork>
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
...
Sec-WebSocket-Version: 25
</artwork>
</figure>
<t>The response from the server might look as follows:</t>
<figure>
<artwork>
HTTP/1.1 400 Bad Request
...
Sec-WebSocket-Version: 13, 8, 7
</artwork>
</figure>
<t>Note that the last response from the server might also look like:</t>
<figure>
<artwork>
HTTP/1.1 400 Bad Request
...
Sec-WebSocket-Version: 13
Sec-WebSocket-Version: 8, 7
</artwork>
</figure>
<t>The client now repeats the handshake that conforms to version 13:</t>
<figure>
<artwork>
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
...
Sec-WebSocket-Version: 13
</artwork>
</figure>
</section>
</section>
<section title='Data Framing' anchor='framing'>
<section title='Overview'>
<t>In the WebSocket protocol, data is transmitted using a sequence of
frames. To avoid confusing network intermediaries (such as
intercepting proxies) and for security reasons that are further
discussed in <xref target="masking-reasons" />, a client MUST mask all frames that it
sends to the server (see <xref target="masking"/> for further details).
(Note that masking is done whether or not the WebSocket protocol is running
over TLS.) The
server MUST close the connection upon receiving a frame that is
not masked. In this case, a server MAY send a close frame with a
status code of 1002 (protocol error) as defined in <xref target="closestatus"/>.
A server MUST NOT mask any frames that it sends to the client. A
client MUST close a connection if it detects a masked frame. In
this case, it MAY use the status code 1002 (protocol error) as
defined in <xref target="closestatus"/>. (These rules might be relaxed
in a future specification.)</t>
<t>The base framing protocol defines a frame type with an opcode, a
payload length, and designated locations for extension and application
data, which together define the <spanx style="emph">payload</spanx>
data. Certain bits and opcodes are reserved for future expansion of
the protocol.</t>
<!--////Add something about frame boundaries not necessarily be preserved by intermediaries-->
<t>A data frame MAY be transmitted by either the client or the server
at any time after opening handshake completion and before that endpoint
has sent a close frame (<xref target="closeframe"/>).</t>
</section>
<section title='Base Framing Protocol' anchor='baseframing'>
<t>
This wire format for the data transfer part is described by
the ABNF <xref target='RFC5234'/> given in detail in this section.
(Note that unlike in other sections of this document the ABNF
in this section is operating on groups of bits. The length of
each group of bits is indicated in a comment. When encoded on
the wire the most significant bit is the leftmost in the ABNF).
A high level overview of the framing is given in the following figure.
In a case of conflict between the figure below and the ABNF specified
later in this section, the figure is authoritative.
<vspace blankLines='1'/>
</t>
<figure>
<artwork>
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-------+-+-------------+-------------------------------+
|F|R|R|R| opcode|M| Payload len | Extended payload length |
|I|S|S|S| (4) |A| (7) | (16/64) |
|N|V|V|V| |S| | (if payload len==126/127) |
| |1|2|3| |K| | |
+-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
| Extended payload length continued, if payload len == 127 |
+ - - - - - - - - - - - - - - - +-------------------------------+
| |Masking-key, if MASK set to 1 |
+-------------------------------+-------------------------------+
| Masking-key (continued) | Payload Data |
+-------------------------------- - - - - - - - - - - - - - - - +
: Payload Data continued ... :
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
| Payload Data continued ... |
+---------------------------------------------------------------+
</artwork>
</figure>
<t>
<list style="hanging">
<t hangText="FIN:">1 bit
<vspace blankLines="1"/>
Indicates that this is the final fragment in a message. The first
fragment MAY also be the final fragment.
</t>
<t hangText="RSV1, RSV2, RSV3:">1 bit each
<vspace blankLines="1"/>
MUST be 0 unless an extension is negotiated which defines
meanings for non-zero values. If a nonzero value is received and
none of the negotiated extensions defines the meaning of such a
nonzero value, the receiving endpoint MUST <spanx
style='emph'>Fail the WebSocket Connection</spanx>.
</t>
<t hangText="Opcode:">4 bits
<vspace blankLines="1"/>
Defines the interpretation of the payload data. If an unknown
opcode is received, the receiving endpoint MUST
<spanx style='emph'>Fail the WebSocket Connection</spanx>.
The following values are defined.
<list style='symbols'>
<t>%x0 denotes a continuation frame</t>
<t>%x1 denotes a text frame</t>
<t>%x2 denotes a binary frame</t>
<t>%x3-7 are reserved for further non-control frames</t>
<t>%x8 denotes a connection close</t>
<t>%x9 denotes a ping</t>
<t>%xA denotes a pong</t>
<t>%xB-F are reserved for further control frames</t>
</list>
</t>
<t hangText="Mask:">1 bit
<vspace blankLines="1"/>
Defines whether the payload data is masked. If set to 1, a
masking key is present in masking-key, and this is used to unmask
the payload data as per <xref target="masking" />. All frames sent
from client to server have this bit set to 1.
</t>
<t hangText="Payload length:">7 bits, 7+16 bits, or 7+64 bits
<vspace blankLines="1"/>
The length of the payload data, in bytes: if 0-125, that is the
payload length. If 126, the following 2 bytes interpreted as a
16 bit unsigned integer are the payload length. If 127, the
following 8 bytes interpreted as a 64-bit unsigned integer (the
most significant bit MUST be 0)
are the payload length. Multibyte length quantities are expressed
in network byte order. Note that in all case the minimal number
of bytes MUST be used to encode the length, for example the length
of a 124 byte long string can't be encoded as the sequence
126, 0, 124. The payload length is the length of the
extension data + the length of the application data. The length
of the extension data may be zero, in which case the payload
length is the length of the application data.
</t>
<t hangText="Masking-key:">0 or 4 bytes
<vspace blankLines="1"/>
All frames sent from the client to the server are masked by a
32-bit value that is contained within the frame. This field is
present if the mask bit is set to 1, and is absent if the mask
bit is set to 0. See <xref target="masking" /> for
further information on client-to-server masking.
</t>
<t hangText="Payload data:">(x+y) bytes
<vspace blankLines="1"/>
The payload data is defined as extension data concatenated with
application data.
</t>
<!--////Is this actually correct?-->
<t hangText="Extension data:">x bytes
<vspace blankLines="1"/>
The extension data is 0 bytes unless an extension
has been negotiated. Any extension MUST specify the length of the
extension data, or how that length may be calculated, and how
the extension use MUST be negotiated during the opening
handshake. If present, the extension data is included in the
total payload length.
</t>
<t hangText="Application data:">y bytes
<vspace blankLines="1"/>
Arbitrary application data, taking up the remainder of the frame
after any extension data. The length of the application data is
equal to the payload length minus the length of the extension
data.
</t>
</list>
</t>
<t>The base framing protocol is formally defined by the following ABNF <xref target='RFC5234'/>. It is important to note that the representation of this data is binary, not ASCII characters. As such, a field with a length of 1 bit that takes values %x0 / %x1 is represented as a single bit whose value is 0 or 1, not a full byte (octet) that stands for the characters "0" or "1" in the ASCII encoding. A field with a length of 4 bits with values between %x0-F again is represented by 4 bits, again NOT by an ASCII character or full byte (octet) with these values. <xref target="RFC5234" /> does not specify a
character encoding - " Rules resolve into a string of terminal values,
sometimes called characters. In ABNF, a character is merely a non-negative
integer. In certain contexts, a specific mapping (encoding) of values into a
character set (such as ASCII) will be specified." Here, the specified
encoding is a binary encoding where each terminal value is encoded in the
specified number of bits, which varies for each field. </t>
<figure height="" suppress-title="false" width="" alt="" title="" align="left">
<artwork type="abnf" height="" name="" width="" alt="" align="left" xml:space="preserve"><![CDATA[
ws-frame = frame-fin ; 1 bit in length
frame-rsv1 ; 1 bit in length
frame-rsv2 ; 1 bit in length
frame-rsv3 ; 1 bit in length
frame-opcode ; 4 bits in length
frame-masked ; 1 bit in length
frame-payload-length ; 7 bits in length
[ frame-masking-key ] ; 16 or 64 bits in length
frame-payload-data ; n * 8 bits in length,
; where n >= 0
frame-fin = %x0 ; more frames of this message follow
/ %x1 ; final frame of this message
; 1 bit in length
frame-rsv1 = %x0 / %x1
; 1 bit in length, MUST be 0 unless negotiated
; otherwise
frame-rsv2 = %x0 / %x1
; 1 bit in length, MUST be 0 unless negotiated
; otherwise
frame-rsv3 = %x0 / %x1
; 1 bit in length, MUST be 0 unless negotiated
; otherwise
frame-opcode = frame-opcode-non-control /
frame-opcode-control
frame-opcode-non-control= %x1 ; text frame
/ %x2 ; binary frame
/ %x3-7
; reserved for further non-control frames
frame-opcode-control = %x8 ; connection close
/ %x9 ; ping
/ %xA ; pong
/ %xB-F ; reserved for further control frames
; 4 bits in length
frame-masked = %x0
; frame is not masked, no frame-masking-key
/ %x1
; frame is masked, frame-masking-key present
; 1 bit in length
frame-payload-length = %x00-7D
/ %x7E frame-payload-length-16
/ %x7F frame-payload-length-63
; 7 bits in length
frame-payload-length-16 = %x0000-FFFF ; 16 bits in length
frame-payload-length-63 = %x0000000000000000-7FFFFFFFFFFFFFFF
; 64 bits in length
frame-masking-key = 4( %0x00-FF )
; present only if frame-masked is 1
; 32 bits in length
frame-payload-data = (frame-masked-extension-data
frame-masked-application-data)
; frame-masked 1
/ (frame-unmasked-extension-data
frame-unmasked-application-data)
; frame-masked 0
frame-masked-extension-data = *( %x00-FF )
; reserved for future extensibility
; n*8 bits in length , where n >= 0
frame-masked-application-data = *( %x00-FF )
; n*8 bits in length, where n >= 0
frame-unmasked-extension-data = *( %x00-FF )
; reserved for future extensibility
; n*8 bits in length, where n >= 0
frame-unmasked-application-data = *( %x00-FF )
; n*8 bits in length, where n >= 0
]]></artwork></figure>
<t>
</t>
</section>
<section title='Client-to-Server Masking' anchor="masking">
<t>A masked frame MUST have the field frame-masked set to 1, as defined
in <xref target="baseframing" />.
</t>
<t>The masking key is contained completely within the frame, as defined
in <xref target="baseframing" /> as frame-masking-key. It is used to
mask the payload data defined in the same section as frame-payload-data,
which includes extension and application data.</t>
<t>The masking key is a 32-bit value chosen at random by the client.
When preparing a masked frame, the client MUST pick a fresh
masking key from the set of allowed 32-bit values. The masking key needs to
be unpredictable, thus the masking key MUST be derived from a strong source
of entropy, and the masking key for a given frame MUST NOT make it simple
for a server/proxy to predict the masking key for a subsequent frame.
The unpredictability of the masking key is essential to
prevent the author of malicious applications from selecting the
bytes that appear on the wire. RFC 4086 <xref
target='RFC4086'/> discusses what entails a suitable source of entropy
for security-sensitive applications.</t>
<t> The masking does not affect the length
of the payload data. To convert masked data into unmasked data, or vice
versa, the following algorithm is applied. The same algorithm applies
regardless of the direction of the translation - e.g. the same steps are
applied to mask the data as to unmask the data.</t>
<t>Octet i of the transformed data ("transformed-octet-i")
is the XOR of octet i of the original
data ("original-octet-i") with octet at index i modulo 4 of the
masking key ("masking-key-octet-j"):</t>
<figure>
<artwork>
<![CDATA[
j = i MOD 4
transformed-octet-i = original-octet-i XOR masking-key-octet-j
]]>
</artwork>
</figure>
<t>The payload length, indicated in the framing as frame-payload-length,
does NOT include the length of the masking key. It is the length of the
payload data, e.g. the number of bytes following the masking key.</t>
</section>
<section title="Fragmentation" anchor='fragmentation'>
<t>
The primary purpose of fragmentation is to allow sending a message
that is of unknown size when the message is started without having
to buffer that message. If messages couldn't be fragmented,
then an endpoint would have to buffer the entire message so its
length could be counted before first byte is sent. With
fragmentation, a server or intermediary may choose a reasonable size
buffer, and when the buffer is full write a fragment to the network.
</t>
<t>
A secondary use-case for fragmentation is for multiplexing, where it
is not desirable for a large message on one logical channel to
monopolize the output channel, so the MUX needs to be free to split
the message into smaller fragments to better share the output
channel. (Note that the multiplexing extension is not described in this
document.)
</t>
<t>Unless specified otherwise by an extension, frames have no semantic
meaning. An intermediary might coalesce and/or split frames, if no extensions
were negotiated by the client and the server, or if some extensions
were negotiated, but the intermediary understood all the extensions
negotiated and knows how to coalesce and/or split frames in presence
of these extensions. One implication of this is that in absence of extensions
senders and receivers must not depend on presence of specific frame boundaries.</t>
<t>The following rules apply to fragmentation:
<list style="symbols">
<t>An unfragmented message consists of a single frame with the FIN
bit set (<xref target='baseframing'/>) and an opcode other than 0.</t>
<t>A fragmented message consists of a single frame with the FIN
bit clear and an opcode other than 0, followed by zero or more
frames with the FIN bit clear and the opcode set to 0, and
terminated by a single frame with the FIN bit set and an opcode of
0. A fragmented message is conceptually equivalent to a single
larger message whose payload is equal to the concatenation of the
<!--////Alexey: Strictly speaking this should be the plural of "payload data".
But maybe saying concatenation of application data is better?-->
payloads of the fragments in order, however in the presence of
extensions this may not hold true as the extension defines the
interpretation of the extension data present. For instance,
extension data may only be present at the beginning of the first
fragment and apply to subsequent fragments, or there may be
extension data present in each of the fragments that applies only to
that particular fragment. In absence of extension data,
the following example demonstrates how fragmentation works.
<vspace blankLines='1'/>
EXAMPLE: For a text message sent as
three fragments, the first fragment would have an opcode of 0x1 and
a FIN bit clear, the second fragment would have an opcode of 0x0 and
a FIN bit clear, and the third fragment would have an opcode of 0x0
and a FIN bit that is set.
</t>
<t>Control frames (see <xref target="controlframes"/>) MAY be injected in the middle of a fragmented
message. Control frames themselves MUST NOT be fragmented.</t>
<t>Message fragments MUST be delivered to the recipient in the order
sent by the sender.</t>
<t>The fragments of one message MUST NOT be interleaved between the
fragments of another message unless an extension has been negotiated
that can interpret the interleaving.</t>
<t>An endpoint MUST be capable of handling control frames in the
middle of a fragmented message.</t>
<t>A sender MAY create fragments of any size for non-control
messages.</t>
<t>Clients and servers MUST support receiving both fragmented and
unfragmented messages.
</t>
<t>As control frames cannot be fragmented, an intermediary MUST NOT
attempt to change the fragmentation of a control frame.</t>
<t>An intermediary MUST NOT change the fragmentation of a message
if any reserved bit values are used and the meaning of these
values is not known to the intermediary.</t>
<!--////Doesn't this mean that an extension might depend on framing?-->
<t>An intermediary MUST NOT change the fragmentation of any message
in the context of a connection where extensions have been negotiated
and the intermediary is not aware of the semantics of the negotiated
extensions.
Similarly, an intermediary that didn't see the WebSocket handshake
(and wasn't notified about its content) that resulted in a WebSocket connection
MUST NOT change the fragmentation of any message of such connection.</t>
<t>
As a consequence of these rules, all fragments of a message are
of the same type, as set by the first fragment's opcode. Since
Control frames cannot be fragmented, the type for all fragments
in a message MUST be either text or binary, or one of the
reserved opcodes.
</t>
</list>
</t>
<t>
<spanx style="emph">Note: if control frames could not be interjected,
the latency of a ping, for example, would be very long if behind a
large message. Hence, the requirement of handling
control frames in the middle of a fragmented message.</spanx>
</t>
<t>
<spanx style="emph">Implementation Note: in absence of any extension
a receiver doesn't have to buffer the whole frame in order to process it.
For example if a streaming API is used, a part of a frame can be delivered
to the application. But note that that assumption might not hold true
for all future WebSocket extensions.</spanx>
</t>
</section>
<section title="Control Frames" anchor="controlframes">
<t>Control frames are identified by opcodes where the most significant
bit of the
opcode is 1. Currently defined opcodes for control frames include 0x8
(Close), 0x9 (Ping), and 0xA (Pong). Opcodes 0xB-0xF are reserved for
further control frames yet to be defined.</t>
<t>Control frames are used to communicate state about the
WebSocket. Control frames can be interjected in the middle of a
fragmented message.
</t>
<t>All control frames MUST have a payload length of 125 bytes or less
and MUST NOT be fragmented.</t>
<section title="Close" anchor="closeframe">
<t>The Close frame contains an opcode of 0x8.</t>
<t>The Close frame MAY contain a body (the "application
data" portion of the frame) that indicates a reason
for closing, such as an endpoint shutting down, an endpoint
having received a frame too large, or an endpoint having
received a frame that does not conform to the format expected
by the other endpoint. If there is a body, the first two bytes of the
body MUST be a 2-byte unsigned integer (in network byte order)
representing a status code with value /code/ defined in
<xref target="status_codes"/>.
Following the
2-byte integer the body MAY contain UTF-8 encoded data with value
/reason/, the interpretation of which is not defined by this
specification. This data is not necessarily human readable, but may
be useful for debugging or passing information relevant to the script
that opened the connection. As the data is not guaranteed to be human
readable, clients MUST NOT show it to end users.</t>
<t>Close frames sent from client to server must be masked as per
<xref target='masking'/>. </t>
<t>The application MUST NOT send any more data frames after sending
a close frame.</t>
<t>If an endpoint receives a Close frame and that endpoint did not
previously send a Close frame, the endpoint MUST send a Close
frame in response. (When sending a Close frame in response the endpoint
typically echos the status code it received.)
It SHOULD do so as soon as practical. An
endpoint MAY delay sending a close frame until its current message is
sent (for instance, if the majority of a fragmented message is already
sent, an endpoint MAY send the remaining fragments before sending a
Close frame). However, there is no guarantee that the endpoint which
has already sent a Close frame will continue to process data.
</t>
<t>After both sending and receiving a close message, an endpoint
considers the WebSocket connection closed, and
MUST close the underlying TCP connection. The server MUST close the
underlying TCP connection immediately; the client SHOULD wait for the
server to close the connection but MAY close the connection at any
time after sending and receiving a close message, e.g. if it has not
received a TCP close from the server in a reasonable time period.</t>
<t>If a client and server both send a Close message at the same time,
both endpoints will have sent and received a Close message and should
consider the WebSocket connection closed and close the underlying
TCP connection.</t>
</section>
<section title="Ping" anchor="pingframe">
<t>The Ping frame contains an opcode of 0x9.</t>
<t>A Ping frame MAY include Application Data.</t>
<t>Upon receipt of a Ping frame, an endpoint MUST send a Pong
frame in response, unless it already received a Close frame.
It SHOULD respond with Pong frame as soon as is practical. Pong
frames are discussed in <xref target='pongframe'/>.
</t>
<t>An endpoint MAY send a Ping frame any time after the connection
is established and before the connection is closed. NOTE: A ping
frame may serve either as a keepalive, or to verify that the
remote endpoint is still responsive.</t>
</section>
<section title="Pong" anchor='pongframe'>
<t>The Pong frame contains an opcode of 0xA.</t>
<t><xref target="pingframe" /> details requirements that apply to both
Ping and Pong frames.</t>
<t>A Pong frame sent in response to a Ping frame must have identical
Application Data as found in the message body of the Ping frame
being replied to.</t>
<t>If an endpoint receives a Ping frame and has not yet sent Pong
frame(s) in response to previous Ping frame(s), the endpoint MAY elect
to send a Pong frame for only the most recently processed Ping frame.
</t>
<t>A Pong frame MAY be sent unsolicited. This serves as a
unidirectional heartbeat. A response to an unsolicited pong is not
expected.</t>
</section>
<!--
<t>A receiver MUST take the following action upon receiving control
frames:
<list style="hanging">
<t hangText="Close:">
<vspace blankLines='1'/>
Upon receipt of a close frame, an endpoint SHOULD send a Close
frame to the remote recipient, if it has not already done so,
deliver a close event to the application if necessary, and then
close the WebSocket.</t>
<t hangText="Ping">
<vspace blankLines='1'/>
Upon receipt of a Ping frame, an endpoint SHOULD send a Pong
response as soon as is practical. The Pong response MUST contain
the payload provided in the Ping frame, though an implementation
MAY truncate the frame at an implementation-defined size which
MUST be at least 8 <spanx style='emph'>(TBD)</spanx> bytes.
<vspace blankLines='1'/>
Ping frames MAY be sent as a keep-alive mechanism, but if so the
interval SHOULD be configurable. </t>
<t hangText="Pong">
<vspace blankLines='1'/>
If a Pong frame is received without a matching Ping frame being
sent, an endpoint MUST drop the connection. Otherwise, the
endpoint SHOULD update any liveness timer it may have for the
connection.</t>
</list>
</t>
-->
</section>
<section title="Data Frames" anchor="dataframes">
<t>
Data frames (e.g. non-control frames) are identified by opcodes where
the most significant bit of the opcode is 0. Currently defined opcodes
for data frames include 0x1 (Text), 0x2 (Binary). Opcodes 0x3-0x7 are
reserved for further non-control frames yet to be defined.
</t>
<t>
Data frames carry application-layer and/or extension-layer data. The
opcode determines the interpretation of the data:
<list style="hanging">
<t hangText="Text">
<vspace blankLines='1'/>
The payload data is text data encoded as UTF-8.
Note that a particular text frame might include a partial UTF-8 sequence,
however the whole message MUST contain valid UTF-8.
Invalid UTF-8 in reassembled messages is handled as described in <xref target='badutf8'/>.
</t>
<t hangText="Binary">
<vspace blankLines='1'/>
The payload data is arbitrary binary data whose interpretation
is solely up to the application layer.
</t>
</list>
</t>
</section>
<section title="Examples">
<t>
<list style="symbols">
<t>
A single-frame unmasked text message
<list style="symbols">
<t>0x81 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains "Hello")</t>
</list>
</t>
<t>
A single-frame masked text message
<list style="symbols">
<t>0x81 0x85 0x37 0xfa 0x21 0x3d 0x7f 0x9f 0x4d 0x51 0x58 (contains "Hello")</t>
</list>
</t>
<t>
A fragmented unmasked text message
<list style="symbols">
<t>0x01 0x03 0x48 0x65 0x6c (contains "Hel")</t>
<t>0x80 0x02 0x6c 0x6f (contains "lo")</t>
</list>
</t>
<t>
Unmasked Ping request and masked Ping response
<list style="symbols">
<t>0x89 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains a body of "Hello", but the contents of the body are arbitrary)</t>
<t>0x8a 0x85 0x37 0xfa 0x21 0x3d 0x7f 0x9f 0x4d 0x51 0x58 (contains a body of "Hello", matching the body of the ping)</t>
</list>
</t>
<t>
256 bytes binary message in a single unmasked frame
<list style="symbols">
<t>0x82 0x7E 0x0100 [256 bytes of binary data]</t>
</list>
</t>
<t>
64KiB binary message in a single unmasked frame
<list style="symbols">
<t>0x82 0x7F 0x0000000000010000 [65536 bytes of binary data]</t>
</list>
</t>
</list>
</t>
</section>
<section title="Extensibility">
<t>The protocol is designed to allow for extensions, which will add
capabilities to the base protocol. The endpoints of a connection MUST
negotiate the use of any extensions during the opening handshake. This
specification provides opcodes 0x3 through 0x7 and 0xB through 0xF, the
extension data field, and the frame-rsv1, frame-rsv2, and frame-rsv3
bits of the frame header for use by extensions. The
negotiation of extensions is discussed in further detail in
<xref target="negotiation" />.
Below are some anticipated uses of extensions. This list is neither
complete nor prescriptive.
<list style="symbols">
<!--////Is this still correct?-->
<t>Extension data may be placed in the payload data before the
application data.</t>
<t>Reserved bits can be allocated for per-frame needs.</t>
<t>Reserved opcode values can be defined.</t>
<t>Reserved bits can be allocated to the opcode field if more
opcode values are needed.</t>
<t>A reserved bit or an "extension" opcode can be defined
which allocates additional bits out of the payload data to define
larger opcodes or more per-frame bits.</t>
</list>
</t>
</section>
</section>
<section title='Sending and Receiving Data'>
<section title='Sending Data' anchor='send_data'>
<t>
To <spanx style='emph'>Send a WebSocket Message</spanx> comprising of
/data/ over a
WebSocket connection, an endpoint MUST perform the following steps.
<list style='numbers'>
<t>The endpoint MUST ensure the WebSocket connection is in the OPEN
state (cf. <xref target="clienths"/> and
<xref target="server_handshake"/>.) If at any point the state of
the WebSocket connection changes, the endpoint MUST abort the
following steps.
</t>
<t>
An endpoint MUST encapsulate the /data/ in a WebSocket frame as
defined in <xref target='baseframing' />. If the
data to be sent is large, or if the data is not available in its
entirety at the point the endpoint wishes to begin sending the
data, the endpoint MAY alternately encapsulate the data in a
series of frames as defined in <xref target='fragmentation'/>.
</t>
<t>The opcode (frame-opcode) of the first frame containing the data
MUST be set to
the appropriate value from <xref target='baseframing' /> for data
that is to be interpreted by the recipient as text or binary data.
</t>
<t>The FIN bit (frame-fin) of the last frame containing the data
MUST be set to 1 as defined in <xref target='baseframing' />.
</t>
<t>If the data is being sent by the client, the frame(s) MUST be
masked as defined in <xref target='masking' />.
</t>
<t>If any extensions (<xref target='extensions' />) have been
negotiated for the WebSocket
connection, additional considerations may apply as per the
definition of those extensions.
</t>
<t>The frame(s) that have been formed MUST be transmitted over the
underlying network connection.
</t>
</list>
</t>
</section>
<section title='Receiving Data' anchor='rcv_data'>
<t>
To receive WebSocket data, an endpoint listens on the underlying
network connection. Incoming data MUST be parsed as WebSocket frames
as defined in <xref target='baseframing' />.
If a control frame (<xref target='controlframes'/>) is received, the
frame MUST be handled as defined by <xref target='controlframes'/>.
Upon receiving a data frame (<xref target='dataframes' />), the
endpoint MUST note the /type/ of the data as defined by the Opcode
(frame-opcode) from <xref target='baseframing' />. The <spanx
style='emph'>Application Data</spanx> from this frame is defined as
the /data/ of the message. If the frame comprises an unfragmented
message (<xref target='fragmentation' />), it is said that <spanx
style='emph'>A WebSocket Message Has Been Received</spanx> with type
/type/ and data /data/. If the frame is part of a fragmented message,
the <spanx style='emph'>Application Data</spanx> of the subsequent
data frames is concatenated to form the /data/. When the last fragment
is received as indicated by the FIN bit (frame-fin), it is said that
<spanx style='emph'>A WebSocket Message Has Been Received</spanx> with
data /data/ (comprised of the concatenation of the <spanx
style='emph'>Application Data</spanx> of the fragments) and type
/type/ (noted from the first frame of the fragmented message).
Subsequent data frames MUST be interpreted as belonging to a new
WebSocket Message.
</t>
<t>Extensions (<xref target='extensions' />) MAY change the semantics of
how data is read, specifically including what comprises a message
boundary. Extensions, in addition to adding "Extension data"
before the "Application data" in a payload, MAY also modify
the "Application data" (such as by compressing it).
</t>
<t>A server MUST remove masking for data frames received from a client as
described in <xref target='masking' />.
</t>
</section>
</section>
<section title='Closing the connection' anchor='closing_connection'>
<section title='Definitions'>
<section title="Close the WebSocket Connection" anchor="close_wsc">
<t>
To <spanx style="emph">Close the WebSocket Connection</spanx>,
an endpoint closes the underlying TCP connection. An endpoint
SHOULD use a method that cleanly closes the TCP connection, as well
as the TLS session, if applicable,
discarding any trailing bytes that may be received. An endpoint
MAY close the connection via any means available when necessary,
such as when under attack.
</t>
<t>
The underlying TCP connection, in most normal cases, SHOULD be
closed first by the server, so that it holds the TIME_WAIT state and
not the client (as this would prevent it from re-opening the
connection for 2 MSL, while there is no corresponding server impact
as a TIME_WAIT connection is immediately reopened upon a new SYN
with a higher seq number). In abnormal cases (such as not having
received a TCP Close from the server after a reasonable amount of
time) a client MAY initiate the TCP Close. As such, when a server is
instructed to <spanx style='emph'>Close the WebSocket
Connection</spanx> it SHOULD initiate a TCP Close immediately, and
when a client is instructed to do the same, it SHOULD wait for a TCP
Close from the server.
</t>
<t>
As an example of how to obtain a clean closure in C
using Berkeley sockets, one would call shutdown() with SHUT_WR
on the socket, call recv() until obtaining a return value of 0
indicating that the peer has also performed an orderly shutdown,
and finally calling close() on the socket.
</t>
</section>
<section title="Start the WebSocket Closing Handshake"
anchor="start_closing">
<t>
To <spanx style="emph">Start the WebSocket Closing
Handshake</spanx> with a status code (<xref
target='status_codes'/>) /code/ and an optional close reason
(<xref target='close_reason'/>) /reason/, an endpoint MUST send a
Close control frame, as
described in <xref target='closeframe' /> whose status code is set
to /code/ and whose close reason is set to /reason/.
Once an endpoint has both sent and received a Close
control frame, that endpoint SHOULD <spanx style='emph'>Close the
WebSocket Connection</spanx> as defined in <xref
target='close_wsc'/>.
</t>
</section>
<section title="The WebSocket Closing Handshake is Started">
<t>
Upon either sending or receiving a Close control frame, it is said
that <spanx style='emph'>The WebSocket Closing Handshake is
Started</spanx> and that the WebSocket connection is in the
CLOSING state.
</t>
</section>
<section title='The WebSocket Connection is Closed' anchor='is_closed'>
<t>
When the underlying TCP connection is closed, it is said that
<spanx style='emph'>The WebSocket Connection is Closed</spanx> and
that the WebSocket connection is in the CLOSED state.
If the tcp connection was
closed after the WebSocket closing handshake was completed,
the WebSocket connection is said to have been closed <spanx
style='emph'>cleanly</spanx>.
</t>
<t>If the WebSocket connection could not be established, it is also
said that <spanx style='emph'>The WebSocket Connection is
Closed</spanx>, but not cleanly.
</t>
</section>
<section title='The WebSocket Connection Close Code' anchor='closecode'>
<t>As defined in <xref target='closeframe' /> and <xref
target='status_codes' />, a Close control frame may contain a
status code indicating a reason for closure. A closing of the
WebSocket connection may be initiated by either endpoint,
potentially simultaneously. <spanx style='emph'>The WebSocket
Connection Close Code</spanx> is defined as the status code (<xref
target='status_codes' />) contained in the first Close control
frame received by the application implementing this protocol.
If this Close control frame
contains no status code, <spanx style='emph'>The WebSocket
Connection Close Code</spanx> is considered to be 1005. If <spanx
style='emph'>The WebSocket Connection is Closed</spanx> and no
Close control frame was received by the endpoint (such as
could occur if the underlying transport connection is lost), <spanx
style='emph'>The WebSocket Connection Close Code</spanx> is
considered to be 1006.
</t>
<t>NOTE: Two endpoints may not agree on the value of <spanx
style='emph'>The WebSocket Connection Close Code</spanx>.
As an example, if the remote endpoint sent a Close frame but the
local application has not yet read the data containing the Close
frame from its socket's receive buffer, and the local
application independently decided to close the connection and send a
Close frame, both endpoints will have sent and received a Close
frame, and will not send further Close frames. Each endpoint will
see the Connection Close Code sent by the other end as the <spanx
style='emph'>WebSocket Connection Close Code</spanx>.
As such, it is possible that the
two endpoints may not agree on the value of <spanx style='emph'>The
WebSocket Connection Close Code</spanx> in the case that both
endpoints <spanx style='emph'>Start the WebSocket Closing
Handshake</spanx> independently and at roughly the same time.
</t>
</section>
<section title='The WebSocket Connection Close Reason'
anchor='close_reason'>
<t>As defined in <xref target='closeframe' /> and <xref
target='status_codes' />, a Close control frame may contain a
status code indicating a reason for closure, followed by UTF-8
encoded data, the interpretation of said data being left to the
endpoints and not defined by this protocol. A closing of the
WebSocket connection may be initiated by either endpoint,
potentially simultaneously. <spanx style='emph'>The WebSocket
Connection Close Reason</spanx> is defined as the UTF-8 encoded
data following the status code (<xref
target='status_codes' />) contained in the first Close control
frame received by the application implementing this protocol.
If there is no such data in
the Close control frame, <spanx style='emph'>The WebSocket
Connection Close Reason</spanx> is the empty string.</t>
<t>NOTE: Following the same logic as noted in <xref target='closecode'
/>, two endpoints may not agree on <spanx
style='emph'>The WebSocket Connection Close Reason</spanx>.
</t>
</section>
<section title='Fail the WebSocket Connection' anchor='fail_ws'>
<t>
Certain algorithms and specifications require an endpoint to
<spanx style='emph'>Fail the WebSocket Connection</spanx>. To
do so, the client MUST <spanx style='emph'>Close the
WebSocket Connection</spanx>, and MAY report the problem
to the user (which would be especially useful for developers) in
an appropriate manner. Similarly, to do so, the server MUST
<spanx style='emph'>Close the WebSocket Connection</spanx>,
and SHOULD log the problem.
</t>
<t>If <spanx style='emph'>The WebSocket Connection is
Established</spanx> prior to the point where the endpoint is
required to <spanx style='emph'>Fail the WebSocket
Connection</spanx>, the endpoint SHOULD send a Close frame with an
appropriate status code <xref target='status_codes'/> before
proceeding to <spanx style='emph'>Close the WebSocket
Connection</spanx>. An endpoint MAY omit sending a Close frame if
it believes the other side is unlikely to be able to receive and
process the close frame, due to the nature of the error that led to
the WebSocket connection being failed in the first place. An
endpoint MUST NOT continue to attempt to process data (including a
responding Close frame) from the remote endpoint after being
instructed to <spanx style='emph'>Fail the WebSocket
Connection</spanx>.
</t>
<t>
Except as indicated above or as specified by the application
layer (e.g. a script using the WebSocket API), clients SHOULD
NOT close the connection.
</t>
</section>
</section>
<section title='Abnormal Closures'>
<section title='Client-Initiated Closure'>
<t>
Certain algorithms, namely during the opening handshake, require
the client to <spanx style='emph'>Fail the WebSocket
Connection</spanx>. To do so, the client MUST
<spanx style='emph'>Fail the WebSocket Connection</spanx> as
defined in <xref target='fail_ws'/>.
</t>
<t>If at any point the underlying transport layer connection is
unexpectedly lost, the client MUST <spanx style='emph'>Fail the
WebSocket Connection</spanx>.
</t>
<t>
Except as indicated above or as specified by the application layer
(e.g. a script using the WebSocket API), clients SHOULD NOT
close the connection.
</t>
<!--
<t>
User agents MUST not convey any failure information to scripts in a way that would allow a script to distinguish the following situations:
<list style='symbols'>
<t>A server whose host name could not be resolved.</t>
<t>A server to which packets could not successfully be routed.</t>
<t>A server that refused the connection on the specified port.</t>
<t>A server that did not complete the opening handshake (e.g. because it was not a WebSocket server).</t>
<t>A WebSocket server that sent a correct opening handshake, but that specified options that caused the client to drop the connection (e.g. the server specified an origin that differed from the script's).</t>
<t>A WebSocket server that abruptly closed the connection after successfully completing the opening handshake.</t>
</list>
</t>
-->
</section>
<section title='Server-Initiated Closure'>
<t>
Certain algorithms require or recommend that the server
<spanx style='emph'>Abort the WebSocket Connection</spanx> during
the opening handshake. To do so, the server MUST simply <spanx
style='emph'>Close the WebSocket Connection</spanx> (<xref
target='close_wsc'/>).
</t>
</section>
<section title='Recovering From Abnormal Closure'>
<t>
Abnormal closures may be caused by any number of reasons. Such
closures could be the result of a transient error, in which case
reconnecting may lead to a good connection and a resumption of
normal operations. Such closures may also be the result of a
nontransient problem, in which case if each deployed client
experiences an abnormal closure and immediately and persistently tries
to reconnect, the server may experience what amounts to a denial of
service attack by a large number of clients trying to reconnect. The
end result of such a scenario could be that the service is unable to
recover, or recovery is made much more difficult, in any sort of timely
manner.
</t>
<t>
To prevent this, clients SHOULD use some form of backoff when
trying to reconnect after abnormal closures as described in this
section.
</t>
<t>
The first reconnect attempt SHOULD be delayed by a random
amount of time. The parameters by which this random delay is chosen
are left to the client to decide; a value chosen randomly between 0
and 5 seconds is a reasonable initial delay though clients MAY choose
a different interval from which to select a delay length based on
implementation experience and particular application.
</t>
<t>
Should the first reconnect attempt fail, subsequent reconnect attempts
SHOULD be delayed by increasingly longer amounts of time, using a
method such as truncated binary exponential backoff.
</t>
</section>
</section>
<section title='Normal Closure of Connections'>
<t>
Servers MAY close the WebSocket connection whenever desired. Clients
SHOULD NOT close the WebSocket connection arbitrarily. In
either case, an endpoint initiates a closure by following the
procedures to <spanx style='emph'>Start the WebSocket Closing
Handshake</spanx> (<xref target='start_closing'/>).
</t>
</section>
<section title='Status Codes' anchor='status_codes'>
<t>
When closing an established connection (e.g. when sending a Close
frame, after the opening handshake has completed), an endpoint MAY
indicate
a reason for closure. The interpretation of this reason by an
endpoint, and the action an endpoint should take given this reason,
are left undefined by this specification. This specification defines
a set of pre-defined status codes, and specifies which ranges may be
used by extensions, frameworks, and end applications. The status
code and any associated textual message are optional components of a
Close frame.
</t>
<section title='Defined Status Codes' anchor="closestatus">
<t>
Endpoints MAY use the following pre-defined status codes
when sending a Close frame.
<list style='hanging'>
<t hangText='1000'>
<vspace blankLines='1'/>
1000 indicates a normal closure, meaning whatever purpose the
connection was established for has been fulfilled.
</t>
<t hangText='1001'>
<vspace blankLines='1'/>
1001 indicates that an endpoint is "going away",
such as a server going down, or a browser having navigated away
from a page.
</t>
<t hangText='1002'>
<vspace blankLines='1'/>
1002 indicates that an endpoint is terminating the connection
due to a protocol error.
</t>
<t hangText='1003'>
<vspace blankLines='1'/>
1003 indicates that an endpoint is terminating the connection
because it has received a type of data it cannot accept (e.g.
an endpoint that understands only text data MAY send this if it
receives a binary message).
</t>
<t hangText='1004'>
<vspace blankLines='1'/>
Reserved. The specific meaning might be defined in the future.
</t>
<t hangText='1005'>
<vspace blankLines='1'/>
1005 is a reserved value and MUST NOT be set as a status code in
a Close control frame by an endpoint. It is designated for use
in applications expecting a status code to indicate that no
status code was actually present.
</t>
<t hangText='1006'>
<vspace blankLines='1'/>
1006 is a reserved value and MUST NOT be set as a status code in
a Close control frame by an endpoint. It is designated for use
in applications expecting a status code to indicate that the
connection was closed abnormally, e.g. without sending or
receiving a Close control frame.
</t>
<t hangText='1007'>
<vspace blankLines='1'/>
1007 indicates that an endpoint is terminating the connection
because it has received data within a message that was not consistent
with the type of the message (e.g., non-UTF-8 <xref target='RFC3629'/>
data within a text message).
</t>
<t hangText='1008'>
<vspace blankLines='1'/>
1008 indicates that an endpoint is terminating the connection
because it has received a message that violates its policy.
This is a generic status code that can be returned when
there is no other more suitable status code (e.g. 1003 or 1009),
or if there is a need to hide specific details about the policy.
</t>
<t hangText='1009'>
<vspace blankLines='1'/>
1009 indicates that an endpoint is terminating the connection
because it has received a message which is too big for it to process.
</t>
<t hangText='1010'>
<vspace blankLines='1'/>
1010 indicates that an endpoint (client) is terminating the connection
because it has expected the server to negotiate one or more extension,
but the server didn't return them in the response message of the WebSocket
handshake. The list of extensions which are needed SHOULD appear in the
/reason/ part of the Close frame.
Note that this status code is not used by the server, because it can
fail the WebSocket handshake instead.
</t>
</list>
</t>
</section>
<section title='Reserved Status Code Ranges'>
<t>
<list style='hanging'>
<t hangText='0-999'>
<vspace blankLines='1'/>
Status codes in the range 0-999 are not used.
</t>
<t hangText='1000-2999'>
<vspace blankLines='1'/>
Status codes in the range 1000-2999 are reserved for
definition by this protocol, its future revisions,
and extensions specified in a permanent and readily
available public specification.
</t>
<t hangText='3000-3999'>
<vspace blankLines='1'/>
Status codes in the range 3000-3999 are reserved for use by
libraries, frameworks and application. These status codes are
registered directly with IANA.
<!--////Alexey: Is this phrase confusing or what?-->
The interpretation of these codes is undefined by this protocol.
</t>
<t hangText='4000-4999'>
<vspace blankLines='1'/>
<!--////Make sure this is in sync with the IANA Considerations section-->
Status codes in the range 4000-4999 are reserved for private
use and thus can't be registered. Such codes can be used by
prior agreements between WebSocket applications.
The interpretation of these codes is undefined by this
protocol.
</t>
</list>
</t>
</section>
</section>
</section>
<section title='Error Handling'>
<section title='Handling Errors in UTF-8 Encoded Data' anchor='badutf8'>
<t>When an endpoint is to interpret a byte stream as UTF-8 but finds that
the byte stream is not in fact a valid UTF-8 stream, that endpoint MUST
<spanx style='emph'>Fail the WebSocket Connection</spanx>.
This rule applies both during the opening handshake and during subsequent
data exchange.
</t>
</section>
</section>
<section title="Extensions" anchor="extensions">
<t>WebSocket clients MAY request extensions to this specification,
and WebSocket servers MAY accept some or all extensions
requested by the client. A server MUST NOT respond with any
extension not requested by the client. If extension
parameters are included in negotiations between the client and the server,
those
parameters MUST be chosen in accordance with the specification of the
extension to which the parameters apply.</t>
<section title="Negotiating Extensions" anchor="negotiation">
<t> A client requests extensions by including a
"Sec-WebSocket-Extensions" header field, which follows the normal
rules for HTTP header fields (see <xref target="RFC2616"/>
section 4.2) and the value of the header field is defined by the following
ABNF <xref target='RFC2616'/>. Note that this section
is using ABNF syntax/rules from <xref target="RFC2616"/>, including
"implied *LWS rule". If a value is
received by either the client or the server during negotiation that does
not conform to the ABNF below, the recipient of such malformed data MUST
immediately <spanx style="emph">Fail the WebSocket Connection</spanx>.
</t>
<figure>
<artwork>
Sec-WebSocket-Extensions = extension-list
extension-list = 1#extension
extension = extension-token *( ";" extension-param )
extension-token = registered-token
registered-token = token
extension-param = token [ "=" (token | quoted-string) ]
;When using the quoted-string syntax variant, the value
;after quoted-string unescaping MUST conform to the
;'token' ABNF.
</artwork>
</figure>
<t>Note that like other HTTP header fields, this header field MAY be split or
combined across multiple lines. Ergo, the following are equivalent:</t>
<figure>
<artwork>
Sec-WebSocket-Extensions: foo
Sec-WebSocket-Extensions: bar; baz=2
</artwork>
</figure>
<t>is exactly equivalent to</t>
<figure>
<artwork>
Sec-WebSocket-Extensions: foo, bar; baz=2
</artwork>
</figure>
<t>Any extension-token used MUST be a registered token
(see <xref target="enr"/>). The parameters supplied with any given extension MUST be
defined for that extension. Note that the client is only offering to
use any advertised extensions, and MUST NOT use them unless the server
indicates that it wishes to use the extension.</t>
<t>Note that the order of extensions is significant. Any interactions
between multiple extensions MAY be defined in the documents defining the
extensions. In the absence of such definition, the interpretation is
that the header fields listed by the client in its request represent a
preference of the header fields it wishes to use, with the first options
listed being most preferable. The extensions listed by the server in
response represent the extensions actually in use for the connection.
Should the extensions
modify the data and/or framing, the order of operations on the data
should be assumed to be the same as the order in which the extensions
are listed in the server's response in the opening handshake.</t>
<t>For example, if there are two extensions "foo" and
"bar", if the header field |Sec-WebSocket-Extensions| sent by the
server has the value "foo, bar" then operations on the data will be
made as bar(foo(data)), be those changes to the data itself (such as
compression) or changes to the framing that may "stack".</t>
<t>Non-normative examples of acceptable extension header fields (note that long lines are folded for readability):</t>
<figure>
<artwork>
Sec-WebSocket-Extensions: deflate-stream
Sec-WebSocket-Extensions: mux; max-channels=4; flow-control,
deflate-stream
Sec-WebSocket-Extensions: private-extension
</artwork>
</figure>
<t>A server accepts one or more extensions by including a
|Sec-WebSocket-Extensions| header field containing one or more
extensions which were requested by the client. The interpretation of any
extension parameters, and what constitutes a valid response by a server
to a requested set of parameters by a client, will be defined by each
such extension.</t>
</section>
<section title="Known Extensions">
<t>Extensions provide a mechanism for implementations to opt-in to
additional protocol features. This document doesn't define any
extension but implementations MAY use extensions defined
separately.</t>
</section>
</section>
<section title='Security Considerations' anchor="securityconsiderations">
<t>This section describes some security considerations applicable to the WebSocket protocol.
Specific security considerations are described in subsections of this section.</t>
<section title="Non-Browser Clients">
<t>Many threats anticipated by the WebSocket protocol protect from malicious
JavaScript running inside a trusted application such as a web browser,
for example checking of the "Origin" header field (see below).
See <xref target="secmodel"/> for additional details.
Such assumptions don't hold true in the case of a more capable client.
</t>
<t>While this protocol is intended to be used by scripts in Web pages,
it can also be used directly by hosts. Such hosts are acting on their own behalf,
and can therefore send fake "Origin" header fields, misleading the server.
Servers should therefore be careful about assuming that they are talking directly
to scripts from known origins, and must consider that they might be accessed in
unexpected ways. In particular, a server should not trust that any input is valid.</t>
<t>EXAMPLE: For example, if the server uses input as part of SQL queries, all input text should be escaped before being passed to the SQL server, lest the server be susceptible to SQL injection.</t>
</section>
<section title="Origin Considerations">
<t>Servers that are not intended to process input from any Web page but only for certain
sites SHOULD verify the "Origin" field is an origin they expect.
If the origin indicated is unacceptable to the server, then it SHOULD respond to the WebSocket
handshake with a reply containing HTTP 403 Forbidden status code.
<!--////Alexey"that value" is ambiguous. Is this a good advice anyway?
Servers that only accept input from one origin can just send back that value in
the "Sec-WebSocket-Accept" header field, without bothering to check
the client's value.
-->
</t>
<t>
<vspace blankLines='1'/>
</t>
<t>
The "Origin" header field protects from the attack cases
when the untrusted party is typically the author of a JavaScript
application that is executing in the context of the trusted client. The client
itself can contact the server and via the mechanism of the
"Origin" header field, determine whether to extend those
communication privileges to the JavaScript application.
The intent is not to prevent non-browsers from establishing
connections, but rather to ensure that trusted browsers under the control of
potentially malicious JavaScript cannot fake a WebSocket
handshake.
</t>
</section>
<section title='Attacks On Infrastructure (Masking)' anchor='masking-reasons'>
<t>
In addition to endpoints being the target of attacks via WebSockets,
other parts of web infrastructure, such as proxies, may be the subject
of an attack.
</t>
<t>
As this protocol was being developed, an experiment was
conducted to demonstrate a class of attacks on proxies that
led to the poisoning of caching proxies deployed in the wild <xref target="TALKING"/>.
The general form of the attack was to establish a connection
to a server under the "attacker's" control,
perform an UPGRADE on the HTTP connection similar to what
the WebSocket protocol does to establish a connection, and
to subsequently send data over that UPGRADEd connection that
looked like a GET request for a specific known resource
(which in an attack would likely be something like a widely
deployed script for tracking hits, or a resource on an
ad-serving network). The remote server would respond with
something that looked like a response to the fake GET request,
and this response would be cached by a nonzero percentage of
deployed intermediaries, thus poisioning the cache. The net
effect of this attack would be that if a user could be
convinced to visit a website the attacker controlled, the
attacker could potentially poison the cache for that user
and other users behind the same cache and run malicious
script on other origins, compromising the web security model.
</t>
<t>
To avoid such attacks on deployed intermediaries, it is not
sufficient to prefix application supplied data with framing that is not
compliant HTTP, as it is not possible to exhaustively discover and test
that each nonconformant intermediary does not skip such non HTTP
framing and act incorrectly on the frame payload. Thus the defence
adopted is to mask all data from the client to the server, so that the
remote script (attacker) does not have control over how the data being
sent appears on the wire, and thus cannot construct a message that
could be misinterpreted by an intermediary as an HTTP request.
</t>
<t>
Clients MUST choose a new masking key for each frame, using
an algorithm that cannot be predicted by end applications that
provide data. For example, each masking could be drawn from
a cryptographically strong random number generator.
If the same key is used, or a decipherable pattern
exists for how the next key is chosen, the attacker can send
a message that, when masked, could appear to be an HTTP
request (by taking the message the attacker wishes to see
on the wire, and masking it with the next masking key to be
used, when the client applies the masking key it will
effectively unmask the data.)
</t>
<t>
It is also necessary that once the transmission of a frame
from a client has begun, the payload (application supplied
data) of that frame must not be capable of being modified by
the application. Otherwise, an attacker could send a long
frame where the initial data was a known value (such as all
zeros), compute the masking key being used upon receipt of
the first part of the data, and then modify
the data that is yet to be sent in the frame to appear as an
HTTP request when masked. (This is essentially the same
problem described in the previous paragraph with using a
known or predictable masking key.) If additional data is to
be sent or data to be sent is somehow changed, that new or
changed data must be sent in a new frame and thus with a
new masking key. In short, once transmission of a frame
begins, the contents must not be modifiable by the remote
script (application).
</t>
<t>
The threat model being protected against is one in which the
client sends data that appears to be a HTTP request. As such,
the channel that needs to be masked is the data from the
client to the server. The data from the server to the client
can be made to look like a response, but to accomplish this
request the client must also be able to forge a request. As
such, it was not deemed necessary to mask data in both
directions (the data from the server to the client is not
masked).
</t>
<!--////The following text might not be valid if masking is not optional?-->
<t>
Despite the protection provided by masking, non-compliant HTTP proxies
will still be vulnerable to poisoning attacks of this type by clients
and servers that do not apply masking.
</t>
</section>
<!--////Does this text need changing?
Add a pointer to how a max frame size (and/or message size) can be advertised-->
<section title='Implementation-Specific Limits'>
<t>Implementations which have implementation- and/or platform-specific
limitations regarding the frame size or total message size after reassembly
from multiple frames MUST protect themselves against exceeding those limits.
(For example, a malicious endpoint can try to exhaust its peer's memory or
mount a denial of service attack by sending either a single big frame
(e.g. of size 2**60), or by sending a long stream
of small frames which are a part of a fragmented message.)
Such an implementation SHOULD impose limit on frame sizes
and the total message size after reassembly from multiple frames.</t>
</section>
<section title='WebSocket client authentication'>
<t>This protocol doesn't prescribe any particular way that servers can authenticate clients
during the WebSocket handshake. The WebSocket server can use any client authentication mechanism
available to a generic HTTP server, such as Cookies, HTTP Authentication, or TLS authentication.
</t>
</section>
<section title='Connection confidentiality and integrity'>
<t>Communications confidentiality and integrity is provided by running
the WebSocket protocol over TLS (wss URIs). WebSocket implementations
MUST support TLS, and SHOULD employ it when communicating with
their peers.</t>
<t>
For connections using TLS, the amount of benefit provided by
TLS depends greatly on the strength of the algorithms negotiated during
the TLS handshake. For example some TLS cipher mechanisms don't provide
connection confidentiality. To achieve reasonable levels of protections, clients
should use only Strong TLS algorithms. "Web Security Context: User
Interface Guidelines" <xref target='W3C.REC-wsc-ui-20100812'/>
discusses what constitutes Strong TLS algorithms.
<xref target='RFC5246'/> provides additional guidance in Appendix A.5 and
Appendix D.3.
</t>
</section>
<section title='Handling of invalid data'>
<t>
Incoming data MUST always be validated by both clients and servers.
If at any time an endpoint is faced with data that it does not understand,
or that violates some criteria by which the endpoint determines safety of input,
or when the endpoint sees an opening handshake that does not correspond to
the values it is expecting (e.g. incorrect path or origin in the client request),
the endpoint MAY drop the TCP connection. If the invalid data received after
a successful WebSocket handshake, the endpoint SHOULD send a Close frame with an
appropriate status code <xref target='status_codes'/> before
proceeding to <spanx style='emph'>Close the WebSocket Connection</spanx>.
Use of a Close frame with an appropriate status code can help in diagnosing
the problem.
If the invalid data is sent during the WebSocket handshake the server SHOULD
return an appropriate HTTP <xref target='RFC2616'/> status code.
</t>
<t>
<vspace blankLines='1'/>
</t>
<t>A common class of security problems arise when sending text data using using
the wrong encoding. This protocol specifies that messages with a Text data type
(as opposed to Binary or other types) contain UTF-8 encoded data. Although the length
is still indicated and applications implementing this protocol should use the length
to determine where the frame actually ends, sending data in an improper encoding may
still break assumptions applications built on top of this protocol may make,
leading from anything to misinterpretation of data to loss of data to potential
security bugs.</t>
</section>
<section title='Use of SHA-1 by the WebSocket handshake'>
<t>
The WebSocket handshake described in this document doesn't depend on any security
properties of SHA-1, such as collision resistance or resistance to the
second pre-image attack (as described in <xref target="RFC4270"/>).
</t>
</section>
</section>
<section title='IANA Considerations'>
<section title='Registration of new URI Schemes'>
<section title='Registration of "ws" Scheme' anchor='wsdef'>
<t>
A |ws| URI identifies a WebSocket server and resource name.
<list style='hanging'>
<t hangText='URI scheme name.'>
<vspace blankLines='0'/>ws
</t>
<t hangText='Status.'>
<vspace blankLines='0'/>Permanent.
</t>
<t hangText='URI scheme syntax.'>
<vspace blankLines='0'/>In ABNF <xref target='RFC5234'/> terms using the terminals from the URI specifications: <xref target='RFC5234'/> <xref target='RFC3986'/><vspace blankLines='1'/><figure>
<artwork> "ws:" "//" authority path-abempty [ "?" query ]</artwork>
</figure>
<vspace blankLines='1'/>
The <path-abempty> and <query> <xref target='RFC3986'/> components form the resource name sent to the server to identify the kind of service desired. Other components have the meanings described in RFC3986.
</t>
<t hangText='URI scheme semantics.'>
<vspace blankLines='0'/>The only operation for this scheme is to open a connection using the WebSocket protocol.
</t>
<t hangText='Encoding considerations.'>
<vspace blankLines='0'/>Characters in the host component that are excluded by the syntax
defined above MUST be converted from Unicode to ASCII as specified in
<xref target='RFC3987'/> or its replacement. For the purposes of scheme-based
normalization IDN forms of the host component and their conversions
to punycode are considered equivalent (see Section 5.3.3 of <xref target='RFC3987'/>).
<vspace blankLines='1'/>
Characters in other components that are excluded by the syntax defined above MUST be converted from Unicode to ASCII by first encoding the characters as UTF-8 and then replacing the corresponding bytes using their percent-encoded form as defined in the URI and IRI specifications. <xref target='RFC3986'/> <xref target='RFC3987'/>
</t>
<t hangText='Applications/protocols that use this URI scheme name.'>
<vspace blankLines='0'/>WebSocket protocol.
</t>
<t hangText='Interoperability considerations.'>
<vspace blankLines='0'/>Use of WebSocket requires use of HTTP version 1.1 or higher.
</t>
<t hangText='Security considerations.'>
<vspace blankLines='0'/>See "Security considerations" section above.
</t>
<t hangText='Contact.'>
<vspace blankLines='0'/>HYBI WG <hybi@ietf.org>
</t>
<t hangText='Author/Change controller.'>
<vspace blankLines='0'/>IETF <iesg@ietf.org>
</t>
<t hangText='References.'>
<vspace blankLines='0'/>RFC XXXX
</t>
</list>
</t>
</section>
<section title='Registration of "wss" Scheme' anchor='wssdef'>
<t>
A |wss| URI identifies a WebSocket server and resource name, and indicates that traffic over that connection is to be protected via TLS (including standard benefits of TLS such as data confidentiality and integrity, and endpoint authentication).
<list style='hanging'>
<t hangText='URI scheme name.'>
<vspace blankLines='0'/>wss
</t>
<t hangText='Status.'>
<vspace blankLines='0'/>Permanent.
</t>
<t hangText='URI scheme syntax.'>
<vspace blankLines='0'/>In ABNF <xref target='RFC5234'/> terms using the terminals from the URI specifications: <xref target='RFC5234'/> <xref target='RFC3986'/><vspace blankLines='1'/><figure>
<artwork> "wss:" "//" authority path-abempty [ "?" query ]</artwork>
</figure>
<vspace blankLines='1'/>
The <path-abempty> and <query> components form the resource name sent to the server to identify the kind of service desired. Other components have the meanings described in RFC3986.
</t>
<t hangText='URI scheme semantics.'>
<vspace blankLines='0'/>The only operation for this scheme is to open a connection using the WebSocket protocol, encrypted using TLS.
</t>
<t hangText='Encoding considerations.'>
<vspace blankLines='0'/>Characters in the host component that are excluded by the syntax
defined above MUST be converted from Unicode to ASCII as specified in
<xref target='RFC3987'/> or its replacement. For the purposes of scheme-based
normalization IDN forms of the host component and their conversions
to punycode are considered equivalent (see Section 5.3.3 of <xref target='RFC3987'/>).
<vspace blankLines='1'/>
Characters in other components that are excluded by the syntax defined above MUST be converted from Unicode to ASCII by first encoding the characters as UTF-8 and then replacing the corresponding bytes using their percent-encoded form as defined in the URI and IRI specification. <xref target='RFC3986'/> <xref target='RFC3987'/>
</t>
<t hangText='Applications/protocols that use this URI scheme name.'>
<vspace blankLines='0'/>WebSocket protocol over TLS.
</t>
<t hangText='Interoperability considerations.'>
<vspace blankLines='0'/>Use of WebSocket requires use of HTTP version 1.1 or higher.
</t>
<t hangText='Security considerations.'>
<vspace blankLines='0'/>See "Security considerations" section above.
</t>
<t hangText='Contact.'>
<vspace blankLines='0'/>HYBI WG <hybi@ietf.org>
</t>
<t hangText='Author/Change controller.'>
<vspace blankLines='0'/>IETF <iesg@ietf.org>
</t>
<t hangText='References.'>
<vspace blankLines='0'/>RFC XXXX
</t>
</list>
</t>
</section>
</section>
<section title='Registration of the "WebSocket" HTTP Upgrade Keyword'>
<t>This section defines a keyword for registration in the "HTTP
Upgrade Tokens" registry as per RFC 2817
<xref target='RFC2817'/>.
<list style='hanging'>
<t hangText='Name of token.'>
<vspace blankLines='0'/>WebSocket
</t>
<t hangText='Author/Change controller.'>
<vspace blankLines='0'/>IETF <iesg@ietf.org>
</t>
<t hangText='Contact.'>
<vspace blankLines='0'/>HYBI <hybi@ietf.org>
</t>
<t hangText='References.'>
<vspace blankLines='0'/>RFC XXXX
</t>
</list>
</t>
</section>
<section title='Registration of new HTTP Header Fields'>
<section title='Sec-WebSocket-Key'>
<t>
This section describes a header field for registration in the Permanent Message Header Field Registry. <xref target='RFC3864'/>
</t>
<t>
<list style='hanging'>
<t hangText='Header field name'>
<vspace blankLines='0'/>Sec-WebSocket-Key
</t>
<t hangText='Applicable protocol'>
<vspace blankLines='0'/>http
</t>
<t hangText='Status'>
<vspace blankLines='0'/>standard
</t>
<t hangText='Author/Change controller'>
<vspace blankLines='0'/>IETF
</t>
<t hangText='Specification document(s)'>
<vspace blankLines='0'/>RFC XXXX
</t>
<t hangText='Related information'>
<vspace blankLines='0'/>This header field is only used for WebSocket opening handshake.
</t>
</list>
</t>
<t>The |Sec-WebSocket-Key| header field is used in the WebSocket opening handshake.
It is sent from the client to the server to provide part of the information used by
the server to prove that it received a valid WebSocket opening handshake.
This helps ensure that the server does not accept connections from non-WebSocket
clients (e.g. HTTP clients) that are being abused to send data to unsuspecting
WebSocket servers.</t>
<t>The |Sec-WebSocket-Key| header field MUST NOT appear more than once in an HTTP request.</t>
</section>
<section title='Sec-WebSocket-Extensions' anchor='swe'>
<t>
This section describes a header field for registration in the Permanent Message Header Field Registry. <xref target='RFC3864'/>
</t>
<t>
<list style='hanging'>
<t hangText='Header field name'>
<vspace blankLines='0'/>Sec-WebSocket-Extensions
</t>
<t hangText='Applicable protocol'>
<vspace blankLines='0'/>http
</t>
<t hangText='Status'>
<vspace blankLines='0'/>standard
</t>
<t hangText='Author/Change controller'>
<vspace blankLines='0'/>IETF
</t>
<t hangText='Specification document(s)'>
<vspace blankLines='0'/>RFC XXXX
</t>
<t hangText='Related information'>
<vspace blankLines='0'/>This header field is only used for WebSocket opening handshake.
</t>
</list>
</t>
<t>The |Sec-WebSocket-Extensions| header field is used in the WebSocket opening handshake.
It is initially sent from the client to the server, and then subsequently sent from
the server to the client, to agree on a set of protocol-level extensions to use for
the duration of the connection.</t>
<t>The |Sec-WebSocket-Extensions| header field MAY appear multiple times in an HTTP request
(which is logically the same as a single |Sec-WebSocket-Extensions| header field that contains all values.
However the |Sec-WebSocket-Extensions| header field MUST NOT appear more than once in an HTTP response.</t>
</section>
<section title='Sec-WebSocket-Accept'>
<t>
This section describes a header field for registration in the Permanent Message Header Field Registry. <xref target='RFC3864'/>
</t>
<t>
<list style='hanging'>
<t hangText='Header field name'>
<vspace blankLines='0'/>Sec-WebSocket-Accept
</t>
<t hangText='Applicable protocol'>
<vspace blankLines='0'/>http
</t>
<t hangText='Status'>
<vspace blankLines='0'/>standard
</t>
<t hangText='Author/Change controller'>
<vspace blankLines='0'/>IETF
</t>
<t hangText='Specification document(s)'>
<vspace blankLines='0'/>RFC XXXX
</t>
<t hangText='Related information'>
<vspace blankLines='0'/>This header field is only used for WebSocket opening handshake.
</t>
</list>
</t>
<t>The |Sec-WebSocket-Accept| header field is used in the WebSocket opening handshake.
It is sent from the server to the client to confirm that the server is willing to initiate
the WebSocket connection.</t>
<t>The |Sec-WebSocket-Accept| header MUST NOT appear more than once in an HTTP response.</t>
</section>
<section title='Sec-WebSocket-Protocol' anchor='swp'>
<t>
This section describes a header field for registration in the Permanent Message Header Field Registry. <xref target='RFC3864'/>
</t>
<t>
<list style='hanging'>
<t hangText='Header field name'>
<vspace blankLines='0'/>Sec-WebSocket-Protocol
</t>
<t hangText='Applicable protocol'>
<vspace blankLines='0'/>http
</t>
<t hangText='Status'>
<vspace blankLines='0'/>standard
</t>
<t hangText='Author/Change controller'>
<vspace blankLines='0'/>IETF
</t>
<t hangText='Specification document(s)'>
<vspace blankLines='0'/>RFC XXXX
</t>
<t hangText='Related information'>
<vspace blankLines='0'/>This header field is only used for WebSocket opening handshake.
</t>
</list>
</t>
<t>The |Sec-WebSocket-Protocol| header field is used in the WebSocket opening handshake.
It is sent from the client to the server and back from the server to the client to confirm
the subprotocol of the connection. This enables scripts to both select a subprotocol and
be sure that the server agreed to serve that subprotocol.</t>
<t>The |Sec-WebSocket-Protocol| header field MAY appear multiple times in an HTTP request
(which is logically the same as a single |Sec-WebSocket-Protocol| header field that contains all values.
However the |Sec-WebSocket-Protocol| header field MUST NOT appear more than once in an HTTP response.</t>
</section>
<section title='Sec-WebSocket-Version'>
<t>
This section describes a header field for registration in the Permanent Message Header Field Registry <xref target='RFC3864'/>.
</t>
<t>
<list style='hanging'>
<t hangText='Header field name'>
<vspace blankLines='0'/>Sec-WebSocket-Version
</t>
<t hangText='Applicable protocol'>
<vspace blankLines='0'/>http
</t>
<t hangText='Status'>
<vspace blankLines='0'/>standard
</t>
<t hangText='Author/Change controller'>
<vspace blankLines='0'/>IETF
</t>
<t hangText='Specification document(s)'>
<vspace blankLines='0'/>RFC XXXX
</t>
<t hangText='Related information'>
<vspace blankLines='0'/>This header field is only used for WebSocket opening handshake.
</t>
</list>
</t>
<t>
The |Sec-WebSocket-Version| header field is used in the WebSocket opening handshake.
It is sent from the client to the server to indicate the protocol version of
the connection. This enables servers to correctly interpret the opening handshake
and subsequent data being sent from the data, and close the connection if the server
cannot interpret that data in a safe manner.
The |Sec-WebSocket-Version| header field is also sent from the server to the client
on WebSocket handshake error, when the version received from the client does not match
a version understood by the server. In such a case the header field includes
the protocol version(s) supported by the server.
</t>
<t>
Note that there is no expectation that higher version numbers are necessarily
backward compatible with lower version numbers.
</t>
<t>The |Sec-WebSocket-Version| header field MAY appear multiple times in an HTTP response
(which is logically the same as a single |Sec-WebSocket-Version| header field that contains all values.
However the |Sec-WebSocket-Version| header field MUST NOT appear more than once in an HTTP request.</t>
</section>
</section>
<section title='WebSocket Extension Name Registry' anchor='enr'>
<t>
This specification requests the creation of a new IANA registry for
WebSocket Extension names to be used with the WebSocket protocol in
accordance with the principles set out in RFC 5226
<xref target='RFC5226'/>.
</t>
<t>As part of this registry IANA will maintain the following
information:
<list style='hanging'>
<t hangText='Extension Identifier'>
<vspace blankLines='0'/>The identifier of the extension, as will
be used in the Sec-WebSocket-Extension header field registered in
<xref target='swe'/> of this specification. The value must
conform to the requirements for an extension-token as defined in
<xref target='negotiation'/> of this specification.
</t>
<t hangText='Extension Common Name'>
<vspace blankLines='0'/>The name of the extension, as the
extension is generally referred to.
</t>
<t hangText='Extension Definition'>
<vspace blankLines='0'/>A reference to the document in which the
extension being used with the WebSocket protocol is defined.
</t>
<t hangText='Known Incompatible Extensions'>
<vspace blankLines='0'/>A list of extension identifiers with which
this extension is known to be incompatible.
</t>
</list>
</t>
<t>WebSocket Extension names are to be subject to "First Come First Served"
IANA registration policy <xref target='RFC5226'/>.
</t>
<t>There are no initial values in this registry.
</t>
</section>
<section title='WebSocket Subprotocol Name Registry' anchor='spr'>
<t>
This specification requests the creation of a new IANA registry for
WebSocket Subprotocol names to be used with the WebSocket protocol in
accordance with the principles set out in RFC 5226
<xref target='RFC5226'/>.
</t>
<t>As part of this registry IANA will maintain the following
information:
<list style='hanging'>
<t hangText='Subprotocol Identifier'>
<vspace blankLines='0'/>The identifier of the subprotocol, as will
be used in the Sec-WebSocket-Protocol header field registered in
<xref target='swp'/> of this specification. The value must
conform to the requirements given in
<xref target='swp-defined'/> of
<xref target='clienths'/> of this specification, namely the
value must be a token as defined by RFC 2616 <xref target='RFC2616'/>.
</t>
<t hangText='Subprotocol Common Name'>
<vspace blankLines='0'/>The name of the subprotocol, as the
subprotocol is generally referred to.
</t>
<t hangText='Subprotocol Definition'>
<vspace blankLines='0'/>A reference to the document in which the
subprotocol being used with the WebSocket protocol is defined.
</t>
</list>
</t>
<t>WebSocket Subprotocol names are to be subject to "First Come First
Served" IANA registration policy <xref target='RFC5226'/>.
</t>
</section>
<section title='WebSocket Version Number Registry'>
<t>
This specification requests the creation of a new IANA registry for
WebSocket Version Numbers to be used with the WebSocket protocol in
accordance with the principles set out in RFC 5226
<xref target='RFC5226'/>.
</t>
<t>As part of this registry IANA will maintain the following
information:
<list style='hanging'>
<t hangText='Version Number'>
<vspace blankLines='0'/>The version number to be used in the
Sec-WebSocket-Version as specified in <xref target='clienths'/> of
this specification. The value must be a non negative integer in the
range between 0 and 255 (inclusive).
</t>
<t hangText='Reference'>
<vspace blankLines='0'/>The RFC requesting a new version number.
</t>
</list>
</t>
<t>WebSocket Version Numbers are to be subject to "IETF Review"
IANA registration policy <xref target='RFC5226'/>.
In order to improve interoperability with intermediate versions
published in Internet Drafts, version numbers associated with such drafts
might be registered in this registry. Note that "IETF Review"
applies to registrations corresponding to Internet Drafts.
</t>
<t>IANA is asked to add initial values to the registry, with suggested
numerical values as these have been used in past versions of this
protocol.
<figure>
<artwork>
Version Number | Reference
-+----------------+-----------------------------------------+-
| 0 + draft-ietf-hybi-thewebsocketprotocol-00 |
-+----------------+-----------------------------------------+-
| 1 + draft-ietf-hybi-thewebsocketprotocol-01 |
-+----------------+-----------------------------------------+-
| 2 + draft-ietf-hybi-thewebsocketprotocol-02 |
-+----------------+-----------------------------------------+-
| 3 + draft-ietf-hybi-thewebsocketprotocol-03 |
-+----------------+-----------------------------------------+-
| 4 + draft-ietf-hybi-thewebsocketprotocol-04 |
-+----------------+-----------------------------------------+-
| 5 + draft-ietf-hybi-thewebsocketprotocol-05 |
-+----------------+-----------------------------------------+-
| 6 + draft-ietf-hybi-thewebsocketprotocol-06 |
-+----------------+-----------------------------------------+-
| 7 + draft-ietf-hybi-thewebsocketprotocol-07 |
-+----------------+-----------------------------------------+-
| 8 + draft-ietf-hybi-thewebsocketprotocol-08 |
-+----------------+-----------------------------------------+-
| 9 + Reserved |
-+----------------+-----------------------------------------+-
| 10 + Reserved |
-+----------------+-----------------------------------------+-
| 11 + Reserved |
-+----------------+-----------------------------------------+-
| 12 + Reserved |
-+----------------+-----------------------------------------+-
| 13 + RFCXXXX (RFC Editor: please update) |
-+----------------+-----------------------------------------+-
</artwork>
</figure>
</t>
</section>
<section title='WebSocket Close Code Number Registry'>
<t>
This specification requests the creation of a new IANA registry for
WebSocket Connection Close Code Numbers in
accordance with the principles set out in RFC 5226
<xref target='RFC5226'/>.
</t>
<t>As part of this registry IANA will maintain the following
information:
<list style='hanging'>
<t hangText='Status Code'>
<vspace blankLines='0'/>The Status Code which denotes a reason for
a WebSocket connection closure as per <xref
target='status_codes'/> of this document. The status code is an
integer number between 1000 and 4999 (inclusive).
</t>
<t hangText='Meaning'>
<vspace blankLines='0'/>The meaning of the status code.
Each status code has to have a unique meaning.
</t>
<t hangText='Contact'>
<vspace blankLines='0'/>A contact for the entity reserving the
status code.
</t>
<t hangText='Reference'>
<vspace blankLines='0'/>The stable document requesting the status
codes and defining their meaning. This is required for status codes in the
range 1000-2999, and recommended for status codes in the range 3000-3999.
</t>
</list>
</t>
<t>WebSocket Close Code Numbers are to be subject to different
registration requirements depending on their range. Unless otherwise
specified, requests are subject to "Standards Action"
IANA registration policy <xref target='RFC5226'/>. Requests for
status codes for use by this protocol, its subsequent versions or
extensions are subject to any one of "Standards Action",
"Specification Required" (which implies "Designated Expert") or "IESG Review"
IANA registration policies and should be granted status codes
in the range 1000-2999. Requests for status codes for use by libraries,
frameworks and applications are subject to "First Come First Served"
IANA registration policy and should be granted in the range 3000-3999.
<!--////Is this range needed?-->
The range of status codes from 4000-4999 is designated for Private Use.
Requests should indicate whether they are requesting
status codes for use by the WebSocket protocol (or a future version of
the protocol) or by extensions, or by libraries/frameworks/applications.
</t>
<t>IANA is asked to add initial values to the registry, with suggested
numerical values as these have been used in past versions of this
protocol.
<figure>
<artwork>
|Status Code | Meaning | Contact | Reference |
-+------------+-----------------+---------------+-----------|
| 1000 | Normal Closure | hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
| 1001 | Going Away | hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
| 1002 | Protocol error | hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
| 1003 | Unsupported Data| hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
| 1004 | ---Reserved---- | hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
| 1005 | No Status Rcvd | hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
| 1006 | Abnormal Closure| hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
| 1007 | Invalid frame | hybi@ietf.org | RFC XXXX |
| | payload data | | |
-+------------+-----------------+---------------+-----------|
| 1008 | Policy Violation| hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
| 1009 | Message Too Big | hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
| 1010 | Mandatory Ext. | hybi@ietf.org | RFC XXXX |
-+------------+-----------------+---------------+-----------|
</artwork>
</figure>
</t>
</section>
<section title='WebSocket Opcode Registry'>
<t>
This specification requests the creation of a new IANA registry for
WebSocket Opcodes in
accordance with the principles set out in RFC 5226
<xref target='RFC5226'/>.
</t>
<t>As part of this registry IANA will maintain the following
information:
<list style='hanging'>
<t hangText='Opcode'>
<vspace blankLines='0'/>The opcode denotes the frame type of the
WebSocket frame, as defined in <xref target='baseframing'/>.
The status code is an integer number between 0 and 15, inclusive.
</t>
<t hangText='Meaning'>
<vspace blankLines='0'/>The meaning of the opcode code.
</t>
<t hangText='Reference'>
<vspace blankLines='0'/>The specification requesting the opcode.
</t>
</list>
</t>
<t>WebSocket Opcode numbers are subject to "Standards Action"
IANA registration policy <xref target='RFC5226'/>.
</t>
<t>IANA is asked to add initial values to the registry, with suggested
numerical values as these have been used in past versions of this
protocol.
<figure>
<artwork>
|Opcode | Meaning | Reference |
-+--------+-------------------------------------+-----------|
| 0 | Continuation Frame | RFC XXXX |
-+--------+-------------------------------------+-----------|
| 1 | Text Frame | RFC XXXX |
-+--------+-------------------------------------+-----------|
| 2 | Binary Frame | RFC XXXX |
-+--------+-------------------------------------+-----------|
| 8 | Connection Close Frame | RFC XXXX |
-+--------+-------------------------------------+-----------|
| 9 | Ping Frame | RFC XXXX |
-+--------+-------------------------------------+-----------|
| 10 | Pong Frame | RFC XXXX |
-+--------+-------------------------------------+-----------|
</artwork>
</figure>
</t>
</section>
<section title='WebSocket Framing Header Bits Registry'>
<t>
This specification requests the creation of a new IANA registry for
WebSocket Framing Header Bits in
accordance with the principles set out in RFC 5226
<xref target='RFC5226'/>. This registry controls assignment of the
bits marked RSV1, RSV2, and RSV3 in <xref target='baseframing'/>.
</t>
<t>These bits are reserved for future versions or extensions of this
specification.</t>
<t>WebSocket Framing Header Bits assignments are subject to "Standards Action"
IANA registration policy <xref target='RFC5226'/>.
</t>
</section>
</section>
<section title='Using the WebSocket protocol from Other Specifications'
anchor='otherspecs'>
<t>The WebSocket protocol is intended to be used by another specification to provide a generic mechanism for dynamic author-defined content, e.g. in a specification defining a scripted API.</t>
<t>
Such a specification first needs to <spanx style='emph'>Establish a WebSocket Connection</spanx>, providing that algorithm with:
<list style='symbols'>
<t>The destination, consisting of a /host/ and a /port/.</t>
<t>A /resource name/, which allows for multiple services to be identified at one host and port.</t>
<t>A /secure/ flag, which is true if the connection is to be encrypted, and false otherwise.</t>
<t>
An ASCII serialization of an origin that is being made responsible for the connection. <xref target='I-D.ietf-websec-origin'/>
</t>
<t>Optionally a string identifying a protocol that is to be layered over the WebSocket connection.</t>
</list>
</t>
<t>The /host/, /port/, /resource name/, and /secure/ flag are usually obtained from a URI using the steps to parse a WebSocket URI's components. These steps fail if the URI does not specify a WebSocket.</t>
<t>If at any time the connection is to be closed, then the specification needs to use the <spanx style='emph'>Close the WebSocket Connection</spanx> algorithm (<xref target='close_wsc'/>).</t>
<t><xref target='is_closed'/> defines when <spanx style='emph'>The
WebSocket Connection is Closed</spanx>.</t>
<t>While a connection is open, the specification will need to handle the cases when <spanx style='emph'>A WebSocket Message Has Been Received</spanx> (<xref target='rcv_data'/>).</t>
<t>To send some data /data/ to an open connection, the specification needs to <spanx style='emph'>Send a WebSocket Message</spanx> (<xref target='send_data'/>).</t>
</section>
<section title='Acknowledgements'>
<t>
Special thanks are due to Ian Hickson, who was the original author and editor of this protocol. The initial design of this specification benefitted from the participation of many people in the WHATWG and WHATWG mailing list. Contributions to that specification are not tracked by section, but a list of all who contributed to that specification is given in the WHATWG HTML specification at http://whatwg.org/html5.
</t>
<t>Special thanks also to John Tamplin for providing a significant amount of text for the Data Framing section of this specification.</t>
<t>Special thanks also to Adam Barth for providing a significant amount of text and background research for the Data Masking section of this specification.</t>
<t>
Special thanks to Lisa Dusseault for the Apps Area review (and for helping to start
this work), Richard Barnes for the Gen-Art review and Magnus Westerlund for
the Transport Area Review. Special thanks to HYBI WG past and present WG chairs
who tirelessly worked behind the scene to move this work toward completion:
Joe Hildebrand, Salvatore Loreto and Gabriel Montenegro. And last but not least,
special thank you to the responsible Area Director Peter Saint-Andre.
</t>
<t>
Thank you to the following people who participated in discussions on the HYBI WG
mailing list and contributed ideas and/or provided detailed reviews (the list is likely
to be incomplete):
Greg Wilkins, John Tamplin, Willy Tarreau, Maciej Stachowiak, Jamie Lokier,
Scott Ferguson, Bjoern Hoehrmann, Julian Reschke, Dave Cridland, Andy Green,
Eric Rescorla, Inaki Baz Castillo, Martin Thomson, Roberto Peon, Patrick McManus,
Zhong Yu, Bruce Atherton, Takeshi Yoshino, Martin J. Duerst, James Graham,
Simon Pieters, Roy T. Fielding, Mykyta Yevstifeyev, Len Holgate, Paul Colomiets,
Piotr Kulaga, Brian Raymor, Jan Koehler, Joonas Lehtolahti, Sylvain Hellegouarch,
Stephen Farrell, Sean Turner, Pete Resnick, Peter Thorson, Joe Mason, John Fallows,
Alexander Philippou.
Note that people listed above didn't necessarily endorse the end result of this work.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include='reference.ANSI.X3-4.1986.xml'?>
<!--RFC Editor: please upgrade this to FIPS-180-3-->
<?rfc include='reference.FIPS.180-2.2002.xml'?>
<?rfc include='reference.RFC.1928.xml'?> <!--SOCKS5-->
<?rfc include='reference.RFC.2119.xml'?>
<?rfc include='reference.RFC.2616.xml'?>
<?rfc include='reference.RFC.2817.xml'?> <!--HTTPS. This is Ok as a DownRef.-->
<?rfc include='reference.RFC.2818.xml'?> <!--HTTPS. This is Ok as a DownRef.-->
<?rfc include='reference.RFC.3629.xml'?>
<?rfc include='reference.RFC.3864.xml'?>
<?rfc include='reference.RFC.3986.xml'?>
<?rfc include='reference.RFC.3987.xml'?>
<?rfc include='reference.RFC.4086.xml'?>
<?rfc include='reference.RFC.5246.xml'?>
<?rfc include='reference.RFC.6066.xml'?> <!--Common TLS extensions-->
<?rfc include='reference.RFC.4648.xml'?> <!--base64-->
<?rfc include='reference.RFC.5226.xml'?>
<?rfc include='reference.RFC.5234.xml'?>
<?rfc include='reference.I-D.draft-ietf-websec-origin-05.xml'?>
<!--
<reference anchor='WEBADDRESSES' target='http://www.w3.org/html/wg/href/draft'>
<front>
<title>Web addresses in HTML 5</title>
<author initials='D.' surname='Connolly' fullname='Dan Connolly'>
<organization>Midwest Web Sense LLC and W3C</organization>
</author>
<author initials='C. M.' surname='Sperberg-McQueen' fullname='C. M. Sperberg-McQueen'>
<organization>Black Mesa Technologies LLC</organization>
</author>
<date day="21" month="May" year="2009"/>
</front>
</reference>
-->
</references>
<references title="Informative References">
<reference anchor='WSAPI' target='http://dev.w3.org/html5/websockets/'>
<front>
<title>The Web Sockets API</title>
<author initials='I.E.' surname='Hickson' fullname='Ian Hickson'>
<organization>Google, Inc.</organization>
</author>
<date day="18" month="August" year="2010"/>
</front>
</reference>
<?rfc include='reference.RFC.4122.xml'?> <!-- GUIDs. Does a better reference exist? -->
<?rfc include='reference.RFC.6265.xml'?> <!-- Cookie -->
<?rfc include='reference.RFC.5321.xml'?> <!--SMTP-->
<?rfc include='reference.RFC.6202.xml'?>
<?rfc include='reference.RFC.4270.xml'?>
<?rfc include='reference.W3C.REC-wsc-ui-20100812.xml'?>
<reference anchor='TALKING' target='http://www.adambarth.com/papers/2011/huang-chen-barth-rescorla-jackson.pdf'>
<front>
<title>Talking to Yourself for Fun and Profit</title>
<author initials='L-S.' surname='Huang' fullname='Lin-Shung Huang'>
<organization>Carnegie Mellon University</organization>
</author>
<author initials='E. Y.' surname='Chen' fullname='Eric Y. Chen'>
<organization>Carnegie Mellon University</organization>
</author>
<author initials='A.' surname='Barth' fullname='Adam Barth'>
<organization>Google, Inc.</organization>
</author>
<author initials='E.' surname='Rescorla' fullname='Eric Rescorla'>
<organization>RTFM</organization>
</author>
<date year="2010"/>
</front>
</reference>
<reference anchor='XMLHttpRequest' target='http://www.w3.org/TR/XMLHttpRequest/'>
<front>
<title>XMLHttpRequest</title>
<author initials='A.' surname='van Kesteren' fullname='Anne van Kesteren' role="editor">
<organization>Opera Software ASA</organization>
</author>
<date day="3" month="August" year="2010"/>
</front>
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 08:25:27 |