HyBi Working Group I. Fette
Internet-Draft Google, Inc.
Intended status: Standards Track April 22, 2011
Expires: October 24, 2011
The WebSocket protocol
draft-ietf-hybi-thewebsocketprotocol-07
Abstract
The WebSocket protocol enables two-way communication between a user
agent 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 initial
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).
Please send feedback to the hybi@ietf.org mailing list.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 24, 2011.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Protocol overview . . . . . . . . . . . . . . . . . . . . 4
1.3. Opening handshake . . . . . . . . . . . . . . . . . . . . 6
1.4. Closing handshake . . . . . . . . . . . . . . . . . . . . 8
1.5. Design philosophy . . . . . . . . . . . . . . . . . . . . 9
1.6. Security model . . . . . . . . . . . . . . . . . . . . . . 10
1.7. Relationship to TCP and HTTP . . . . . . . . . . . . . . . 10
1.8. Establishing a connection . . . . . . . . . . . . . . . . 11
1.9. Subprotocols using the WebSocket protocol . . . . . . . . 11
2. Conformance requirements . . . . . . . . . . . . . . . . . . . 13
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 13
3. WebSocket URIs . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1. Parsing WebSocket URIs . . . . . . . . . . . . . . . . . . 15
3.2. Constructing WebSocket URIs . . . . . . . . . . . . . . . 16
3.3. Valid WebSocket URIs . . . . . . . . . . . . . . . . . . . 16
4. Data Framing . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.2. Base Framing Protocol . . . . . . . . . . . . . . . . . . 17
4.3. Client-to-Server Masking . . . . . . . . . . . . . . . . . 20
4.4. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 21
4.5. Control Frames . . . . . . . . . . . . . . . . . . . . . . 23
4.5.1. Close . . . . . . . . . . . . . . . . . . . . . . . . 23
4.5.2. Ping . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.5.3. Pong . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.6. Data Frames . . . . . . . . . . . . . . . . . . . . . . . 24
4.7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.8. Extensibility . . . . . . . . . . . . . . . . . . . . . . 25
5. Opening Handshake . . . . . . . . . . . . . . . . . . . . . . 27
5.1. Client Requirements . . . . . . . . . . . . . . . . . . . 27
5.2. Server-side requirements . . . . . . . . . . . . . . . . . 31
5.2.1. Reading the client's opening handshake . . . . . . . . 32
5.2.2. Sending the server's opening handshake . . . . . . . . 32
6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 36
6.1. Handling errors in UTF-8 from the server . . . . . . . . . 36
6.2. Handling errors in UTF-8 from the client . . . . . . . . . 36
7. Closing the connection . . . . . . . . . . . . . . . . . . . . 37
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7.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 37
7.1.1. Close the WebSocket Connection . . . . . . . . . . . . 37
7.1.2. Start the WebSocket Closing Handshake . . . . . . . . 37
7.1.3. The WebSocket Connection Is Closed . . . . . . . . . . 37
7.1.4. Fail the WebSocket Connection . . . . . . . . . . . . 37
7.2. Abnormal closures . . . . . . . . . . . . . . . . . . . . 37
7.2.1. Client-initiated closure . . . . . . . . . . . . . . . 38
7.2.2. Server-initiated closure . . . . . . . . . . . . . . . 38
7.3. Normal closure of connections . . . . . . . . . . . . . . 38
7.4. Status codes . . . . . . . . . . . . . . . . . . . . . . . 38
7.4.1. Defined Status Codes . . . . . . . . . . . . . . . . . 38
7.4.2. Reserved status code ranges . . . . . . . . . . . . . 39
8. Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.1. Negotiating extensions . . . . . . . . . . . . . . . . . . 41
8.2. Known extensions . . . . . . . . . . . . . . . . . . . . . 42
8.2.1. Compression . . . . . . . . . . . . . . . . . . . . . 42
9. Security considerations . . . . . . . . . . . . . . . . . . . 44
10. IANA considerations . . . . . . . . . . . . . . . . . . . . . 46
10.1. Registration of ws: scheme . . . . . . . . . . . . . . . . 46
10.2. Registration of wss: scheme . . . . . . . . . . . . . . . 47
10.3. Registration of the "WebSocket" HTTP Upgrade keyword . . . 48
10.4. Sec-WebSocket-Key . . . . . . . . . . . . . . . . . . . . 48
10.5. Sec-WebSocket-Extensions . . . . . . . . . . . . . . . . . 49
10.6. Sec-WebSocket-Accept . . . . . . . . . . . . . . . . . . . 50
10.7. Sec-WebSocket-Origin . . . . . . . . . . . . . . . . . . . 50
10.8. Sec-WebSocket-Protocol . . . . . . . . . . . . . . . . . . 51
10.9. Sec-WebSocket-Version . . . . . . . . . . . . . . . . . . 51
11. Using the WebSocket protocol from other specifications . . . . 53
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 54
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
13.1. Normative References . . . . . . . . . . . . . . . . . . . 55
13.2. Informative References . . . . . . . . . . . . . . . . . . 56
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 57
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1. Introduction
1.1. Background
_This section is non-normative._
Historically, creating an instant messenger chat client as a Web
application has required an abuse of HTTP to poll the server for
updates while sending upstream notifications as distinct HTTP
calls.[RFC6202]
This results in a variety of problems:
o 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.
o The wire protocol has a high overhead, with each client-to-server
message having an HTTP header.
o The client-side script is forced to maintain a mapping from the
outgoing connections to the incoming connection to track replies.
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. [WSAPI]
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.
1.2. Protocol overview
_This section is non-normative._
The protocol has two parts: a handshake, and then the data transfer.
The handshake from the client looks as follows:
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GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Origin: http://example.com
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 7
The handshake from the server looks as follows:
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
Sec-WebSocket-Protocol: chat
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 [RFC2616].
After the leading line in both cases come an unordered set of header
fields. The meaning of these header fields is specified in Section 5
of this document. Additional header fields may also be present, such
as cookies [I-D.ietf-httpstate-cookie] required to identify the user.
The format and parsing of headers is as defined in [RFC2616].
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.
Clients and servers, after a successful handshake, transfer data back
and forth in conceptual units referred to in this specification as
"messages". 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. The websocket message does
not necessarily correspond to a particular network layer framing, as
a fragmented message may be coalesced, or vice versa, e.g. by an
intermediary.
Data is sent on the wire in the form of frames that have an
associated type. A message is composed of one or more frames, all of
which contain the same type of data. Broadly speaking, there are
types for textual data, which is interpreted as UTF-8 [RFC3629] text,
binary data (whose interpretation is left up to the application), and
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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.
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.
1.3. Opening handshake
_This section is non-normative._
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:
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Origin: http://example.com
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 7
Headers in the handshake are sent by the client in a random order;
the order is not meaningful.
The "Request-URI" of the GET method [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.
The client includes the hostname in the Host header of its handshake
as per [RFC2616], so that both the client and the server can verify
that they agree on which host is in use.
Additional headers are used to select options in the WebSocket
protocol. Options available in this version are the subprotocol
selector, |Sec-WebSocket-Protocol|, and |Cookie|, which can used for
sending cookies to the server (e.g. as an authentication mechanism).
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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 of the acceptable protocols and echoes that value in its
handshake to indicate that it has selected that protocol.
Sec-WebSocket-Protocol: chat
The |Sec-WebSocket-Origin| header 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 abort the connection. This header is sent by browser
clients, for non-browser clients this header may be sent if it makes
sense in the context of those clients.
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| or a |form| submission.
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 in the
client handshake:
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
For this header, the server has to take the value (as present in the
header, e.g. the base64-encoded [RFC4648] version minus leading and
trailing whitespace), and concatenate this with the GUID "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, base64-encoded, of this concatenation is
then returned in the server's handshake [FIPS.180-2.2002].
Concretely, if as in the example above, header |Sec-WebSocket-Key|
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, to give the value "s3pPLMBiTxaQ9kYGzzhZRbK+
xOo=". This value would then be echoed in the header |Sec-WebSocket-
Accept|.
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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:
HTTP/1.1 101 Switching Protocols
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.
The |Connection| and |Upgrade| headers complete the HTTP Upgrade.
The |Sec-WebSocket-Accept| header indicates whether the server is
willing to accept the connection. If present, this header 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.
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
These fields are checked by the Web browser when it is acting as a
|WebSocket| client for scripted pages. If the |Sec-WebSocket-Accept|
value does not match the expected value, or if the header is missing,
or if the HTTP status code is not 101, the connection will not be
established and WebSockets frames will not be sent.
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. Web browsers verify
that the server included one of the values as was specified in the
WebSocket client' 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.
Sec-WebSocket-Protocol: chat
The server can also set cookie-related option fields to _set_
cookies, as in HTTP.
1.4. Closing handshake
_This section is non-normative._
The closing handshake is far simpler than the opening handshake.
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Either peer can send a control frame with data containing a specified
control sequence to begin the closing handshake (detailed in
Section 4.5.1). Upon receiving such a frame, the other peer sends a
close frame in response, if it hasn't already sent one. Upon
receiving _that_ control frame, the first peer then closes the
connection, safe in the knowledge that no further data is
forthcoming.
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.
It is safe for both peers to initiate this handshake simultaneously.
The closing handshake is intended to replace 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 man-in-
the-middle proxies and other intermediaries.
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.
1.5. Design philosophy
_This section is non-normative._
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 (HTTP).
Conceptually, WebSocket is really just a layer on top of TCP that
adds a Web "origin"-based security model for browsers; adds an
addressing and protocol naming mechanism to support multiple services
on one port and multiple host names on one IP address; 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; and re-
implements the closing handshake in-band. Other than that, it 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
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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.
The protocol is intended to be extensible; future versions will
likely introduce additional concepts such as multiplexing.
1.6. Security model
_This section is non-normative._
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.
This protocol is intended to fail to establish a connection with
servers of pre-existing protocols like SMTP [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).
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|.
1.7. Relationship to TCP and HTTP
_This section is non-normative._
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.
By default the WebSocket protocol uses port 80 for regular WebSocket
connections and port 443 for WebSocket connections tunneled over TLS
[RFC2818].
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1.8. Establishing a connection
_This section is non-normative._
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.
1.9. Subprotocols using the WebSocket protocol
_This section is non-normative._
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.
These subprotocol names do not need to be registered, but if a
subprotocol is intended to be implemented by multiple independent
WebSocket servers, potential clashes with the names of subprotocols
defined independently can be avoided by using names that contain 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
"example.org's chat protocol", 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.
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
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of extensibility.
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2. Conformance requirements
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.
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this
document are to be interpreted as described in RFC2119. [RFC2119]
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.
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.)
Implementations MAY impose implementation-specific limits on
otherwise unconstrained inputs, e.g. to prevent denial of service
attacks, to guard against running out of memory, or to work around
platform-specific limitations.
The conformance classes defined by this specification are user agents
and servers.
2.1. Terminology
*ASCII* shall mean the character-encoding scheme defined in
[ANSI.X3-4.1986].
*Converting a string to ASCII lowercase* 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).
Comparing two strings in an *ASCII case-insensitive* 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.
The term "URI" is used in this document as defined in [RFC3986].
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When an implementation is required to _send_ 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.
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3. WebSocket URIs
3.1. Parsing WebSocket URIs
The steps to *parse a WebSocket URI's components* from a string /uri/
are as follows. These steps return either a /host/, a /port/, a
/resource name/, and a /secure/ flag, or they fail.
1. If the /uri/ string is not an absolute URI, then fail this
algorithm. [RFC3986]
2. Resolve the /uri/ string using the resolve a Web address
algorithm defined by the Web addresses specification, with the
URI character encoding set to UTF-8. [RFC3629] [RFC3986]
[RFC3987]
NOTE: It doesn't matter what it is resolved relative to, since
we already know it is an absolute URI at this point.
3. If /uri/ does not have a <scheme> component whose value, when
converted to ASCII lowercase, is either "ws" or "wss", then fail
this algorithm.
4. If /uri/ has a <fragment> component, then fail this algorithm.
5. If the <scheme> component of /uri/ is "ws", set /secure/ to
false; otherwise, if the <scheme> component is "wss", set
/secure/ to true; if neither of the above apply, fail this
algorithm.
6. Let /host/ be the value of the <host> component of /uri/,
converted to ASCII lowercase.
7. If /uri/ has a <port> component, then let /port/ be that
component's value; otherwise, there is no explicit /port/.
8. If there is no explicit /port/, then: if /secure/ is false, let
/port/ be 80, otherwise let /port/ be 443.
9. Let /resource name/ be the value of the <path> component (which
might be empty) of /uri/.
10. If /resource name/ is the empty string, set it to a single
character U+002F SOLIDUS (/).
11. If /uri/ has a <query> component, then append a single U+003F
QUESTION MARK character (?) to /resource name/, followed by the
value of the <query> component.
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12. Return /host/, /port/, /resource name/, and /secure/.
3.2. Constructing WebSocket URIs
The steps to *construct a WebSocket URI* from a /host/, a /port/, a
/resource name/, and a /secure/ flag, are as follows:
1. Let /uri/ be the empty string.
2. If the /secure/ flag is false, then append the string "ws://" to
/uri/. Otherwise, append the string "wss://" to /uri/.
3. Append /host/ to /uri/.
4. If the /secure/ flag is false and port is not 80, or if the
/secure/ flag is true and port is not 443, then append the string
":" followed by /port/ to /uri/.
5. Append /resource name/ to /uri/.
6. Return /uri/.
3.3. Valid WebSocket URIs
For a WebSocket URI to be considered valid, the following conditions
MUST hold.
o The /host/ MUST be ASCII-only (i.e. it MUST have been punycode-
encoded [RFC3492] already if necessary, and MUST NOT contain any
characters above U+007E).
o The /resource name/ string MUST be a non-empty string of
characters in the range U+0021 to U+007E and MUST start with a
U+002F SOLIDUS character (/).
Any WebSocket URIs not meeting the above criteria are considered
invalid. A client MUST NOT attempt to make a connection to an
invalid WebSocket URI. A client SHOULD attempt to parse a URI
obtained from any external source (such as a web site or a user)
using the steps specified in Section 3.1 to obtain a valid WebSocket
URI, but MUST NOT attempt to connect with such an unparsed URI, and
instead only use the parsed version and only if that version is
considered valid by the criteria above.
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4. Data Framing
4.1. Overview
In the WebSocket protocol, data is transmitted using a sequence of
frames. Frames sent from the client to the server are masked to
avoid confusing network intermediaries, such as intercepting proxies.
Frames sent from the server to the client are not masked.
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 _payload_ data. Certain
bits and opcodes are reserved for future expansion of the protocol.
As such, in the absence of extensions negotiated during the opening
handshake (Section 5), all reserved bits MUST be 0 and reserved
opcode values MUST NOT be used.
A data frame MAY be transmitted by either the client or the server at
any time after handshake completion and before that endpoint has sent
a close message (Section 4.5.1).
4.2. Base Framing Protocol
This wire format for the data transfer part is described by the ABNF
[RFC5234] given in detail in this section. A high level overview of
the framing is given in the following figure.
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) | (16/63) |
|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 ... |
+---------------------------------------------------------------+
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FIN: 1 bit
Indicates that this is the final fragment in a message. The first
fragment MAY also be the final fragment.
RSV1, RSV2, RSV3: 1 bit each
Must be 0 unless an extension is negotiated which defines meanings
for non-zero values
Opcode: 4 bits
Defines the interpretation of the payload data
Mask: 1 bit
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 Section 4.3. All frames sent from client
to server have this bit set to 1.
Payload length: 7 bits, 7+16 bits, or 7+64 bits
The length of the payload: 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. 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. The length
of this field is always at least 7 bits. If the value of the
first 7 bits is 0-125, the length of this field is 7 bits. If the
value is 126, there exist 16 additional bits with a 16-bit length.
If the value is 127, there exist 64 additional bits with a 63-bit
length (the most significant bit MUST be 0).
Masking-key: 0 or 4 bytes
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 Section 4.3 for further information on client-
to-server masking.
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Payload data: n bytes
The payload data is defined as Extension Data concatenated with
Application Data.
Extension data: n bytes
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 handshake. If
present, the extension data is included in the total payload
length.
Application data: n bytes
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.
The base framing protocol is formally defined by the following ABNF
[RFC5234]:
ws-frame = frame-fin
frame-rsv1
frame-rsv2
frame-rsv3
frame-opcode
frame-masked
frame-payload-length
[ frame-masking-key ]
frame-payload-data
frame-fin = %x0 ; more frames of this message follow
/ %x1 ; final frame of message
frame-rsv1 = %x0 ; 1 bit, MUST be 0
frame-rsv2 = %x0 ; 1 bit, MUST be 0
frame-rsv3 = %x0 ; 1 bit, MUST be 0
frame-opcode = %x0 ; continuation frame
/ %x1 ; text frame
/ %x2 ; binary frame
/ %3-7 ; reserved for further non-control frames
/ %x8 ; connection close
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/ %x9 ; ping
/ %xA ; pong
/ %xB-F ; reserved for further control frames
frame-masked = %x0 ; frame is not masked, no frame-masking-key
= %x1 ; frame is masked, frame-masking-key present
frame-payload-length = %x00-7D
/ %x7E frame-payload-length-16
/ %x7F frame-payload-length-63
frame-payload-length-16 = %x0000-FFFF
frame-payload-length-63 = %x0000000000000000-7FFFFFFFFFFFFFFF
frame-masking-key = <4>( %0x00-FF ) ; present only if frame-masked is 1
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 ) ; to be defined later
frame-masked-application-data = *( %x00-FF )
frame-unmasked-extension-data = *( %x00-FF ) ; to be defined later
frame-unmasked-application-data = *( %x00-FF )
4.3. Client-to-Server Masking
The client MUST mask all frames sent to the server. A server MUST
close the connection upon receiving a frame with the MASK bit set to
0. In this case, a server MAY send a close frame with a status code
of 1002 (protocol error) as defined in Section 7.4.1.
A masked frame MUST have the field frame-masked set to 1, as defined
in Section 4.2.
The masking key is contained completely within the frame, as defined
in Section 4.2 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.
The masking key is a 32-bit value chosen at random by the client.
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
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server to predict the masking key for a subsequent frame.
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.
Octet i of the transformed data ("transformed-octet-i") is the XOR of
octet i of the original data ("original-octet-i") with octet i modulo
4 of the masking key ("masking-key-octet-j"):
j = i MOD 4
transformed-octet-i = original-octet-i XOR masking-key-octet-j
When preparing a masked frame, the client MUST pick a fresh masking
key uniformly at random from the set of allowed 32-bit values. The
unpredictability of the masking-nonce is essential to prevent the
author of malicious application data from selecting the bytes that
appear on the wire.
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.
4.4. Fragmentation
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.
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.
The following rules apply to fragmentation:
o An unfragmented message consists of a single frame with the FIN
bit set and an opcode other than 0.
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o 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. Its
content is the concatenation of the application data (and any
extension data that may be present) from each of those frames in
order. As an example, for a text message sent as three fragments,
the first fragment would have an opcode of 0x4 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.
o Control frames MAY be injected in the middle of a fragmented
message. Control frames themselves MUST NOT be fragmented.
o An endpoint MUST be capable of handling control frames in the
middle of a fragmented message.
o _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._
o A sender MAY create fragments of any size for non control
messages.
o Clients and servers MUST support receiving both fragmented and
unfragmented messages.
o As control frames cannot be fragmented, an intermediary MUST NOT
attempt to change the fragmentation of a control frame.
o 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.
o 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.
o 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.
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4.5. Control Frames
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.
Control frames are used to communicate state about the websocket.
Control frames can be interjected in the middle of a fragmented
message.
All control frames MUST have a payload length of 125 bytes or less
and MUST NOT be fragmented.
4.5.1. Close
The Close message contains an opcode of 0x8.
The Close message 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 message too
large, or an endpoint having received a message 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 integer (in network
byte order) representing a status code defined in Section 7.4.
Following the 2-byte integer the body MAY contain UTF-8 encoded data,
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.
The application MUST NOT send any more data frames after sending a
close message.
If an endpoint receives a Close message and that endpoint did not
previously send a Close message, the endpoint MUST send a Close
message in response. It SHOULD do so as soon as is practical.
After both sending and receiving a close message, an endpoint
considers the websocket connection closed, and SHOULD close the
underlying TCP connection.
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.
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4.5.2. Ping
The Ping message contains an opcode of 0x9.
Upon receipt of a Ping message, an endpoint MUST send a Pong message
in response. It SHOULD do so as soon as is practical. The message
bodies (i.e. both the Extension data (if any) and the Application
data) of the Ping and Pong MUST be the same.
An endpoint MAY send a Ping message any time after the connection is
established and before the connection is closed. NOTE: A ping
message may serve either as a keepalive, or to verify that the remote
endpoint is still responsive.
4.5.3. Pong
The Pong message contains an opcode of 0xA.
Upon receipt of a Ping message, an endpoint MUST send a Pong message
in response. It SHOULD do so as soon as is practical. The message
bodies (i.e. both the Extension data (if any) and the Application
data) of the Ping and Pong MUST be the same. In the case multiple
Pings have been received, a Pong MUST be issued only in response to
the most recent Ping.
A Pong message MAY be sent unsolicited. This serves as a
unidirectional heartbeat. A response to an unsolicited pong is not
expected.
4.6. Data Frames
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.
Data frames carry application-layer or extension-layer data. The
opcode determines the interpretation of the data:
Text
The payload data is text data encoded as UTF-8.
Binary
The payload data is arbitrary binary data whose interpretation is
solely up to the application layer.
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4.7. Examples
_This section is non-normative._
o A single-frame unmasked text message
* 0x81 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains "Hello")
o A single-frame masked text message
* 0x81 0x85 0x37 0xfa 0x21 0x3d 0x7f 0x9f 0x4d 0x51 0x58
(contains "Hello")
o A fragmented unmasked text message
* 0x01 0x03 0x48 0x65 0x6c (contains "Hel")
* 0x80 0x02 0x6c 0x6f (contains "lo")
o Ping request and response
* 0x89 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains a body of "Hello",
but the contents of the body are arbitrary)
* 0x8a 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains a body of "Hello",
matching the body of the ping)
o 256 bytes binary message in a single unmasked frame
* 0x82 0x7E 0x0100 [256 bytes of binary data]
o 64KiB binary message in a single unmasked frame
* 0x82 0x7F 0x0000000000010000 [65536 bytes of binary data]
4.8. Extensibility
The protocol is designed to allow for extensions, which will add
capabilities to the base protocols. The endpoints of a connection
MUST negotiate the use of any extensions during the 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 Section 8.1. Below
are some anticipated uses of extensions. This list is neither
complete nor proscriptive.
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o Extension data may be placed in the payload before the application
data.
o Reserved bits can be allocated for per-frame needs.
o Reserved opcode values can be defined.
o Reserved bits can be allocated to the opcode field if more opcode
values are needed.
o A reserved bit or an "extension" opcode can be defined which
allocates additional bits out of the payload area to define larger
opcodes or more per-frame bits.
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5. Opening Handshake
5.1. Client Requirements
User agents 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 user agent for the purposes of conformance is
considered to include both the handset software and any such agents.
When the user agent is to *establish a WebSocket connection* given
either a WebSocket URI /uri/ or the constituent components of a URI
as specified in Section 11, it MUST meet the following requirements.
In the following text, we will use terms from Section 3 such as
"/host/" and "/secure/ flag" as defined in that section.
1. The WebSocket URI and its components derived by applying the
steps defined in Section 3.3, or if the following algorithm was
supplied with the constituent components as defined in Section 11
then those components provided, MUST be valid according to
Section 3.3. If any of the requirements are not met, the client
MUST fail the WebSocket connection and abort these steps.
2. If the user agent 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 user
agent 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 user agent MUST
serialize them so that there is no more than one connection at a
time running through the following steps.
If the user agent 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 user
agent MUST assume for the purposes of this step that each host
name refers to a distinct remote host, but should instead limit
the total number of simultaneous connections that are not
established to a reasonably low number (e.g., in a Web browser,
to the number of tabs the user has open).
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 making use of this by pausing
before closing the connection, as that will reduce the rate at
which the client reconnects.
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NOTE: There is no limit to the number of established WebSocket
connections a user agent can have with a single remote host.
Servers can refuse to accept connections from hosts with an
excessive number of existing connections, or disconnect resource-
hogging connections when suffering high load.
3. _Proxy Usage_: If the user agent is configured to use a proxy
when using the WebSocket protocol to connect to host /host/
and/or port /port/, then the user agent 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/.
EXAMPLE: For example, if the user agent 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:
CONNECT example.com:80 HTTP/1.1
Host: example.com
If there was a password, the connection might look like:
CONNECT example.com:80 HTTP/1.1
Host: example.com
Proxy-authorization: Basic ZWRuYW1vZGU6bm9jYXBlcyE=
If the user agent 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/.
NOTE: Implementations that do not expose explicit UI for
selecting a proxy for WebSocket connections separate from other
proxies are encouraged to use a SOCKS proxy for WebSocket
connections, if available, or failing that, to prefer the proxy
configured for HTTPS connections over the proxy configured for
HTTP connections.
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 steps to
construct a WebSocket URI as given in Section 3.2.
NOTE: The WebSocket protocol can be identified in proxy
autoconfiguration scripts from the scheme ("ws:" for unencrypted
connections and "wss:" for encrypted connections).
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4. If the connection could not be opened, either because a direct
connection failed or because any proxy used returned an error,
then the user agent MUST fail the WebSocket connection and abort
the connection attempt.
5. If /secure/ is true, the user agent MUST perform a TLS handshake
over the connection [RFC2818]. If this fails (e.g. the server's
certificate could not be verified), then the user agent MUST fail
the WebSocket connection and abort the connection. Otherwise,
all further communication on this channel MUST run through the
encrypted tunnel. [RFC5246]
User agents MUST use the Server Name Indication extension in the
TLS handshake. [RFC6066]
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 a handshake to the server. The handshake consists of an
HTTP upgrade request, along with a list of required and optional
headers. The requirements for this handshake are as follows.
1. The handshake MUST be a valid HTTP request as specified by
[RFC2616].
2. The Method of the request MUST be GET and the HTTP version MUST
be at least 1.1.
For example, if the WebSocket URI is "ws://example.com/chat",
The first line sent should be "GET /chat HTTP/1.1"
3. The request MUST contain a "Request-URI" as part of the GET
method. This MUST match the /resource name/ Section 3.
4. The request MUST contain a "Host" header whose value is equal to
/host/
5. The request MUST contain an "Upgrade" header whose value is
equal to "websocket".
6. The request MUST contain a "Connection" header whose value MUST
include the "Upgrade" token.
7. The request MUST include a header with the name "Sec-WebSocket-
Key". The value of this header MUST be a nonce consisting of a
randomly selected 16-byte value that has been base64-encoded
[RFC3548]. The nonce MUST be selected randomly for each
connection.
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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
would be "AQIDBAUGBwgJCgsMDQ4PEC=="
8. The request MUST include a header with the name "Sec-WebSocket-
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 if the semantics of that client match the use-case
described here for browser clients. The value of this header
MUST be the ASCII serialization of origin of the context in
which the code establishing the connection is running, and MUST
be lower-case. The value MUST NOT contain letters in the range
U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL
LETTER Z) [I-D.ietf-websec-origin].
As an example, if code is running on www.example.com attempting
to establish a connection to ww2.example.com, the value of the
header would be "http://www.example.com".
9. The request MUST include a header with the name "Sec-WebSocket-
Version". The value of this header MUST be 7.
10. The request MAY include a header with the name "Sec-WebSocket-
Protocol". If present, this value indicates the subprotocol(s)
the client wishes to speak. The elements that comprise this
value MUST be non-empty strings with characters in the range
U+0021 to U+007E and MUST all be unique strings. The ABNF for
the value of this header is 1#(token | quoted-string), where the
definitions of constructs and rules are as given in [RFC2616].
11. The request MAY include a header 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 is described in
Section 8.1.
12. The request MAY include headers associated with sending cookies,
as defined by the appropriate specifications
[I-D.ietf-httpstate-cookie].
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:
o If the status code received from the server is not 101, the client
handles the response per HTTP procedures. Otherwise, proceed as
follows.
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o If the response lacks an Upgrade header or the Upgrade header
contains a value that is not an ASCII case-insensitive match for
the value "websocket", the client MUST fail the WebSocket
connection.
o If the response lacks a Connection header or the Connection header
contains a value that is not an ASCII case-insensitive match for
the value "Upgrade", the client MUST fail the WebSocket
connection.
o If the response lacks a Sec-WebSocket-Accept header 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", the client MUST fail the WebSocket connection.
Where the algorithm above requires that a user agent fail the
WebSocket connection, the user agent MAY first read an arbitrary
number of further bytes from the connection (and then discard them)
before actually *failing the WebSocket connection*. Similarly, if a
user agent can show that the bytes read from the connection so far
are such that there is no subsequent sequence of bytes that the
server can send that would not result in the user agent being
required to *fail the WebSocket connection*, the user agent MAY
immediately *fail the WebSocket connection* without waiting for those
bytes.
NOTE: The previous paragraph is intended to make it conforming for
user agents to implement the algorithm in subtly different ways that
are equivalent in all ways except that they terminate the connection
at earlier or later points. For example, it enables an
implementation to buffer the entire handshake response before
checking it, or to verify each field as it is received rather than
collecting all the fields and then checking them as a block.
5.2. Server-side requirements
_This section only applies to servers._
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 conformance 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.
EXAMPLE: For example, a data center might have a server that responds
to WebSocket requests with an appropriate handshake, and then passes
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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.
5.2.1. Reading the client's opening handshake
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.
The client 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, the server MUST abort
the WebSocket connection.
1. An HTTP/1.1 or higher GET request, including a "Request-URI"
[RFC2616] that should be interpreted as a /resource name/
Section 3.
2. A "Host" header containing the server's authority.
3. A "Sec-WebSocket-Key" header with a base64-encoded value that,
when decoded, is 16 bytes in length.
4. A "Sec-WebSocket-Version" header, with a value of 7.
5. Optionally, a "Sec-WebSocket-Origin" header. This header is sent
by all browser clients. A connection attempt lacking this header
SHOULD NOT be interpreted as coming from a browser client.
6. Optionally, a "Sec-WebSocket-Protocol" header, with a list of
values indicating which protocols the client would like to speak,
ordered by preference.
7. Optionally, a "Sec-WebSocket-Extensions" header, with a list of
values indicating which extensions the client would like to
speak. The interpretation of this header is discussed in
Section 8.1.
8. Optionally, other headers, such as those used to send cookies to
a server. Unknown headers MUST be ignored.
5.2.2. Sending the server's opening handshake
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.
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1. If the server supports encryption, 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 handshake) MUST run through the encrypted tunnel.
[RFC5246]
2. Establish the following information:
/origin/
The |Sec-WebSocket-Origin| header 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. For more detail, refer to
Section 9.
/key/
The |Sec-WebSocket-Key| header 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.
/version/
The |Sec-WebSocket-Version| header 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 connection. The server MAY send a non-200
response code with a |Sec-WebSocket-Version| header indicating
the version(s) the server is capable of understanding.
/resource name/
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 [RFC2616] of the GET method.
/subprotocol/
Either a single value or null, representing the subprotocol
the server is ready to use. If the server supports multiple
subprotocols, then the value MUST be derived from the client's
handshake, specifically by selecting one of the values from
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the "Sec-WebSocket-Protocol" 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, and is not
a legal value for this field. The ABNF for the value of this
header is (token | quoted-string), where the definitions of
constructs and rules are as given in [RFC2616].
/extensions/
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 Section 8.1.
3. If the server chooses to accept the incoming connection, it MUST
reply with a valid HTTP response indicating the following.
1. A 101 response code. Such a response could look like
"HTTP/1.1 101 Switching Protocols"
2. A "Sec-WebSocket-Accept" header. The value of this header is
constructed by concatenating /key/, defined above in
Paragraph 2 of Section 5.2.2, 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 this 20-byte hash.
NOTE: As an example, if the value of the "Sec-WebSocket-Key"
header 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.
3. Optionally, a "Sec-WebSocket-Protocol" header, with a value
/subprotocol/ as defined in Paragraph 2 of Section 5.2.2.
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4. Optionally, a "Sec-WebSocket-Extensions" header, with a value
/extensions/ as defined in Paragraph 2 of Section 5.2.2.
This completes the server's handshake. If the server finishes these
steps without aborting the WebSocket connection, 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.
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6. Error Handling
6.1. Handling errors in UTF-8 from the server
When a client is to interpret a byte stream as UTF-8 but finds that
the byte stream is not in fact a valid UTF-8 stream, then any bytes
or sequences of bytes that are not valid UTF-8 sequences MUST be
interpreted as a U+FFFD REPLACEMENT CHARACTER.
6.2. Handling errors in UTF-8 from the client
When a server is to interpret a byte stream as UTF-8 but finds that
the byte stream is not in fact a valid UTF-8 stream, behavior is
undefined. A server could close the connection, convert invalid byte
sequences to U+FFFD REPLACEMENT CHARACTERs, store the data verbatim,
or perform application-specific processing. Subprotocols layered on
the WebSocket protocol might define specific behavior for servers.
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7. Closing the connection
7.1. Definitions
7.1.1. Close the WebSocket Connection
To _Close the WebSocket Connection_, 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.
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.
7.1.2. Start the WebSocket Closing Handshake
To _start the WebSocket closing handshake_, an endpoint MUST send a
Close control frame, as described in Section 4.5.1. Once an endpoint
has both sent and received a Close control frame, that endpoint
SHOULD _Close the WebSocket Connection_ as defined in Section 7.1.1.
7.1.3. The WebSocket Connection Is Closed
When the underlying TCP connection is closed, it is said that _the
WebSocket connection is closed_. If the tcp connection was closed
after the WebSocket closing handshake was completed, the WebSocket
connection is said to have been closed _cleanly_.
7.1.4. Fail the WebSocket Connection
Certain algorithms and specifications require a user agent to _fail
the WebSocket connection_. To do so, the user agent MUST _Close the
WebSocket Connection_, and MAY report the problem to the user (which
would be especially useful for developers) in an appropriate manner.
Except as indicated above or as specified by the application layer
(e.g. a script using the WebSocket API), user agents SHOULD NOT close
the connection.
7.2. Abnormal closures
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7.2.1. Client-initiated closure
Certain algorithms, namely during the initial handshake, require the
user agent to *fail the WebSocket connection*. To do so, the user
agent MUST _Close the WebSocket connection_ as previously defined,
and MAY report the problem to the user via an appropriate mechanism
(which would be especially useful for developers).
Except as indicated above or as specified by the application layer
(e.g. a script using the WebSocket API), user agents SHOULD NOT close
the connection.
7.2.2. Server-initiated closure
Certain algorithms require or recommend that the server _abort the
WebSocket connection_ during the opening handshake. To do so, the
server MUST simply _close the WebSocket connection_ (Section 7.1.1).
7.3. Normal closure of connections
Servers MAY close the WebSocket connection whenever desired. User
agents SHOULD NOT close the WebSocket connection arbitrarily. In
either case, an endpoint initiates a closure by following the
procedures to _start the WebSocket closing handshake_
(Section 7.1.2).
7.4. Status codes
When closing an established connection (e.g. when sending a Close
frame, after the 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.
7.4.1. Defined Status Codes
Endpoints MAY use the following pre-defined status codes when sending
a Close frame.
1000
1000 indicates a normal closure, meaning whatever purpose the
connection was established for has been fulfilled.
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1001
1001 indicates that an endpoint is "going away", such as a server
going down, or a browser having navigated away from a page.
1002
1002 indicates that an endpoint is terminating the connection due
to a protocol error.
1003
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).
1004
1004 indicates that an endpoint is terminating the connection
because it has received a message that is too large.
7.4.2. Reserved status code ranges
0-999
Status codes in the range 0-999 are not used.
1000-1999
Status codes in the range 1000-1999 are reserved for definition by
this protocol.
2000-2999
Status codes in the range 2000-2999 are reserved for use by
extensions.
3000-3999
Status codes in the range 3000-3999 MAY be used by libraries and
frameworks. The interpretation of these codes is undefined by
this protocol. End applications MUST NOT use status codes in this
range.
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4000-4999
Status codes in the range 4000-4999 MAY be used by application
code. The interpretation of these codes is undefined by this
protocol.
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8. Extensions
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.
8.1. Negotiating extensions
A client requests extensions by including a "Sec-WebSocket-
Extensions" header, which follows the normal rules for HTTP headers
(see [RFC2616] section 4.2) and the value of the header is defined by
the following ABNF. Note that unlike other section of the document
this section is using ABNF syntax/rules from [RFC2616].
extension-list = 1#extension
extension = extension-token *( ";" extension-param )
extension-token = registered-token | private-use-token
registered-token = token
private-use-token = "x-" token
extension-param = token [ "=" ( token | quoted-string ) ]
Note that like other HTTP headers, this header MAY be split or
combined across multiple lines. Ergo, the following are equivalent:
Sec-WebSocket-Extensions: foo
Sec-WebSocket-Extensions: bar; baz=2
is exactly equivalent to
Sec-WebSocket-Extensions: foo, bar; baz=2
Any extension-token used MUST either be a registered token
(registration TBD), or have a prefix of "x-" to indicate a private-
use token. 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.
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 headers listed by the client in its
request represent a preference of the headers it wishes to use, with
the first options listed being most preferable. The extensions
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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.
For example, if there are two extensions "foo" and "bar", if the
header |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 thay may "stack".
Non-normative examples of acceptable extension headers:
Sec-WebSocket-Extensions: deflate-stream
Sec-WebSocket-Extensions: mux; max-channels=4; flow-control, deflate-stream
Sec-WebSocket-Extensions: x-private-extension
A server accepts one or more extensions by including a |Sec-
WebSocket-Extensions| header 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.
8.2. Known extensions
Extensions provide a mechanism for implementations to opt-in to
additional protocol features. This section defines the meaning of
well-known extensions but implementations MAY use extensions defined
separately as well.
8.2.1. Compression
The registered extension token for this compression extension is
"deflate-stream".
The extension does not have any per message extension data and it
does not define the use of any WebSocket reserved bits or op codes.
Senders using this extension MUST apply RFC 1951 encodings to all
bytes of the data stream following the handshake including both data
and control messages. The data stream MAY include multiple blocks of
both compressed and uncompressed types as defined by [RFC1951].
Senders MUST NOT delay the transmission of any portion of a WebSocket
message because the deflate encoding of the message does not end on a
byte boundary. The encodings for adjacent messages MAY appear in the
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same byte if no delay in transmission is occurred by doing so.
Historically there have been some confusion and interoperability
problems around the specification of compression algorithms. In this
specification "deflate-stream" requires a [RFC1951] deflate encoding.
It MUST NOT be wrapped in any of the header formats often associated
with RFC 1951 such as "zlib" [RFC1950]. This requirement is given
special attention with this note because of confusion in this area,
the presence of some popular open source libraries that create both
formats under a single API call with confusing naming conventions,
and the fact that the popular HTTP [RFC2616] specification defines
"deflate" compression differently than this specification.
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9. Security considerations
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" 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.
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.
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, and should only respond with the corresponding "Sec-
WebSocket-Origin" if it is an accepted origin. Servers that only
accept input from one origin can just send back that value in the
"Sec-WebSocket-Origin" field, without bothering to check the client's
value.
If at any time a server is faced with data that it does not
understand, or that violates some criteria by which the server
determines safety of input, or when the server sees a handshake that
does not correspond to the values the server is expecting (e.g.
incorrect path or origin), the server SHOULD just disconnect. It is
always safe to disconnect.
The biggest security risk when sending text data using this protocol
is sending data using the wrong encoding. If an attacker can trick
the server into sending data encoded as ISO-8859-1 verbatim (for
instance), rather than encoded as UTF-8, then the attacker could
inject arbitrary frames into the data stream.
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. In particular, an intermediary may interpret a
WebSocket message from a client as a request, and a message from the
server as a response to that request. For instance, an attacker
could get a browser to establish a connection to its server, get the
browser to send a message that looks to an intermediary like a GET
request for a common piece of JavaScript on another domain, and send
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back a message that is interpreted as a cacheable response to that
request, thus poisioning the cache for other users. To prevent this
attack, messages sent from clients are masked on the wire with a 32-
bit value, to prevent an attacker from controlling the bits on the
wire and thus lessen the probability of an attacker being able to
construct a message that can be misinterpreted by a proxy as a non-
WebSocket request.
As mentioned in Section 6.2, servers must be extremely cautious
interpreting invalid UTF-8 data from the client. A naive UTF-8
parsing implementation can result in buffer overflows in the case of
invalid input data.
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10. IANA considerations
10.1. Registration of ws: scheme
A |ws:| URI identifies a WebSocket server and resource name.
URI scheme name.
ws
Status.
Permanent.
URI scheme syntax.
In ABNF terms using the terminals from the URI specifications:
[RFC5234] [RFC3986]
"ws" ":" hier-part [ "?" query ]
The <path> [RFC3986] 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.
URI scheme semantics.
The only operation for this scheme is to open a connection using
the WebSocket protocol.
Encoding considerations.
Characters in the host component that are excluded by the syntax
defined above MUST be converted from Unicode to ASCII by applying
the IDNA ToASCII algorithm to the Unicode host name, with both the
AllowUnassigned and UseSTD3ASCIIRules flags set, and using the
result of this algorithm as the host in the URI. [RFC3490]
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. [RFC3986] [RFC3987]
Applications/protocols that use this URI scheme name.
WebSocket protocol.
Interoperability considerations.
None.
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Security considerations.
See "Security considerations" section above.
Contact.
HYBI WG <hybi@ietf.org>
Author/Change controller.
IETF <iesg@ietf.org>
References.
RFC XXXX
10.2. Registration of wss: scheme
A |wss:| URI identifies a WebSocket server and resource name, and
indicates that traffic over that connection is to be encrypted.
URI scheme name.
wss
Status.
Permanent.
URI scheme syntax.
In ABNF terms using the terminals from the URI specifications:
[RFC5234] [RFC3986]
"wss" ":" hier-part [ "?" query ]
The <path> 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.
URI scheme semantics.
The only operation for this scheme is to open a connection using
the WebSocket protocol, encrypted using TLS.
Encoding considerations.
Characters in the host component that are excluded by the syntax
defined above MUST be converted from Unicode to ASCII by applying
the IDNA ToASCII algorithm to the Unicode host name, with both the
AllowUnassigned and UseSTD3ASCIIRules flags set, and using the
result of this algorithm as the host in the URI. [RFC3490]
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
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the URI and IRI specification. [RFC3986] [RFC3987]
Applications/protocols that use this URI scheme name.
WebSocket protocol over TLS.
Interoperability considerations.
None.
Security considerations.
See "Security considerations" section above.
Contact.
HYBI WG <hybi@ietf.org>
Author/Change controller.
IETF <iesg@ietf.org>
References.
RFC XXXX
10.3. Registration of the "WebSocket" HTTP Upgrade keyword
Name of token.
WebSocket
Author/Change controller.
IETF <iesg@ietf.org>
Contact.
HYBI <hybi@ietf.org>
References.
RFC XXXX
10.4. Sec-WebSocket-Key
This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864]
Header field name
Sec-WebSocket-Key
Applicable protocol
http
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Status
standard
Author/Change controller
IETF
Specification document(s)
RFC XXXX
Related information
This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Key| header is used in the WebSocket 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 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.
10.5. Sec-WebSocket-Extensions
This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864]
Header field name
Sec-WebSocket-Extensions
Applicable protocol
http
Status
standard
Author/Change controller
IETF
Specification document(s)
RFC XXXX
Related information
This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Extensions| header is used in the WebSocket
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.
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10.6. Sec-WebSocket-Accept
This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864]
Header field name
Sec-WebSocket-Accept
Applicable protocol
http
Status
standard
Author/Change controller
IETF
Specification document(s)
RFC XXXX
Related information
This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Accept| header is used in the WebSocket handshake.
It is sent from the server to the client to confirm that the server
is willing to initiate the connection.
10.7. Sec-WebSocket-Origin
This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864]
Header field name
Sec-WebSocket-Origin
Applicable protocol
http
Status
standard
Author/Change controller
IETF
Specification document(s)
RFC XXXX
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Related information
This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Origin| header is used in the WebSocket handshake.
It is sent from the server to the client to confirm the origin of the
script that opened the connection. This enables user agents to
verify that the server is willing to serve the script that opened the
connection.
10.8. Sec-WebSocket-Protocol
This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864]
Header field name
Sec-WebSocket-Protocol
Applicable protocol
http
Status
standard
Author/Change controller
IETF
Specification document(s)
RFC XXXX
Related information
This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Protocol| header is used in the WebSocket
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.
10.9. Sec-WebSocket-Version
This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864]
Header field name
Sec-WebSocket-Version
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Applicable protocol
http
Status
standard
Author/Change controller
IETF
Specification document(s)
RFC XXXX
Related information
This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Version| header is used in the WebSocket
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 handshake and subsequent data being sent from
the data, and close the connection if the server cannot interpret
that data in a safe manner.
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11. Using the WebSocket protocol from other specifications
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.
Such a specification first needs to "establish a WebSocket
connection", providing that algorithm with:
o The destination, consisting of a /host/ and a /port/.
o A /resource name/, which allows for multiple services to be
identified at one host and port.
o A /secure/ flag, which is true if the connection is to be
encrypted, and false otherwise.
o An ASCII serialization of an origin that is being made responsible
for the connection. [I-D.ietf-websec-origin]
o Optionally a string identifying a protocol that is to be layered
over the WebSocket connection.
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.
If a connection can be established, then it is said that the
"WebSocket connection is established".
If at any time the connection is to be closed, then the specification
needs to use the "close the WebSocket connection" algorithm.
When the connection is closed, for any reason including failure to
establish the connection in the first place, it is said that the
"WebSocket connection is closed".
While a connection is open, the specification will need to handle the
cases when "a WebSocket message has been received" with text /data/.
To send some text /data/ to an open connection, the specification
needs to "send /data/ using the WebSocket".
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12. Acknowledgements
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.
Special thanks also to John Tamplin for providing a significant
amount of text for the Data Framing section of this specification.
Special thanks also to Adam Barth for providing a significant amount
of text and background research for the Data Masking section of this
specification.
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13. References
13.1. Normative References
[ANSI.X3-4.1986]
American National Standards Institute, "Coded Character
Set - 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986.
[FIPS.180-2.2002]
National Institute of Standards and Technology, "Secure
Hash Standard", FIPS PUB 180-2, August 2002, <http://
csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf>.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
version 1.3", RFC 1951, May 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003.
[RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, March 2003.
[RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, July 2003.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
September 2004.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
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[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
Extension Definitions", RFC 6066, January 2011.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
13.2. Informative References
[WSAPI] Hickson, I., "The Web Sockets API", August 2010,
<http://dev.w3.org/html5/websockets/>.
[I-D.ietf-httpstate-cookie]
Barth, A., "HTTP State Management Mechanism",
draft-ietf-httpstate-cookie-20 (work in progress),
December 2010.
[I-D.ietf-websec-origin]
Barth, A., "The Web Origin Concept",
draft-ietf-websec-origin-00 (work in progress),
December 2010.
[RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format
Specification version 3.3", RFC 1950, May 1996.
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
October 2008.
[RFC6202] Loreto, S., Saint-Andre, P., Salsano, S., and G. Wilkins,
"Known Issues and Best Practices for the Use of Long
Polling and Streaming in Bidirectional HTTP", RFC 6202,
April 2011.
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Author's Address
Ian Fette
Google, Inc.
Email: ifette+ietf@google.com
URI: http://www.ianfette.com/
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