Internet Engineering Task Force (IETF)                          I. Fette
Request for Comments: 6455                                  Google, Inc.
Category: Standards Track                                    A. Melnikov
ISSN: 2070-1721                                               Isode Ltd.
                                                           December 2011


                         
The WebSocket Protocol

Abstract

   The WebSocket Protocol enables two-way communication between a client
   running untrusted code 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).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6455.

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
   (http://trustee.ietf.org/license-info) in effect on the date of
   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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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Background . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Protocol Overview  . . . . . . . . . . . . . . . . . . . .  5
     1.3.  Opening Handshake  . . . . . . . . . . . . . . . . . . . .  6
     1.4.  Closing Handshake  . . . . . . . . . . . . . . . . . . . .  9
     1.5.  Design Philosophy  . . . . . . . . . . . . . . . . . . . .  9
     1.6.  Security Model . . . . . . . . . . . . . . . . . . . . . . 10
     1.7.  Relationship to TCP and HTTP . . . . . . . . . . . . . . . 11
     1.8.  Establishing a Connection  . . . . . . . . . . . . . . . . 11
     1.9.  Subprotocols Using the WebSocket Protocol  . . . . . . . . 12
   2.  Conformance Requirements . . . . . . . . . . . . . . . . . . . 12
     2.1.  Terminology and Other Conventions  . . . . . . . . . . . . 13
   3.  WebSocket URIs . . . . . . . . . . . . . . . . . . . . . . . . 14
   4.  Opening Handshake  . . . . . . . . . . . . . . . . . . . . . . 14
     4.1.  Client Requirements  . . . . . . . . . . . . . . . . . . . 14
     4.2.  Server-Side Requirements . . . . . . . . . . . . . . . . . 20
       4.2.1.  Reading the Client's Opening Handshake . . . . . . . . 21
       4.2.2.  Sending the Server's Opening Handshake . . . . . . . . 22
     4.3.  Collected ABNF for New Header Fields Used in Handshake . . 25
     4.4.  Supporting Multiple Versions of WebSocket Protocol . . . . 26
   5.  Data Framing . . . . . . . . . . . . . . . . . . . . . . . . . 27
     5.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . 27
     5.2.  Base Framing Protocol  . . . . . . . . . . . . . . . . . . 28
     5.3.  Client-to-Server Masking . . . . . . . . . . . . . . . . . 32
     5.4.  Fragmentation  . . . . . . . . . . . . . . . . . . . . . . 33
     5.5.  Control Frames . . . . . . . . . . . . . . . . . . . . . . 36
       5.5.1.  Close  . . . . . . . . . . . . . . . . . . . . . . . . 36
       5.5.2.  Ping . . . . . . . . . . . . . . . . . . . . . . . . . 37
       5.5.3.  Pong . . . . . . . . . . . . . . . . . . . . . . . . . 37
     5.6.  Data Frames  . . . . . . . . . . . . . . . . . . . . . . . 38
     5.7.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . 38
     5.8.  Extensibility  . . . . . . . . . . . . . . . . . . . . . . 39
   6.  Sending and Receiving Data . . . . . . . . . . . . . . . . . . 39
     6.1.  Sending Data . . . . . . . . . . . . . . . . . . . . . . . 39
     6.2.  Receiving Data . . . . . . . . . . . . . . . . . . . . . . 40
   7.  Closing the Connection . . . . . . . . . . . . . . . . . . . . 41
     7.1.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . 41
       7.1.1.  Close the WebSocket Connection . . . . . . . . . . . . 41
       7.1.2.  Start the WebSocket Closing Handshake  . . . . . . . . 42
       7.1.3.  The WebSocket Closing Handshake is Started . . . . . . 42
       7.1.4.  The WebSocket Connection is Closed . . . . . . . . . . 42
       7.1.5.  The WebSocket Connection Close Code  . . . . . . . . . 42



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       7.1.6.  The WebSocket Connection Close Reason  . . . . . . . . 43
       7.1.7.  Fail the WebSocket Connection  . . . . . . . . . . . . 43
     7.2.  Abnormal Closures  . . . . . . . . . . . . . . . . . . . . 44
       7.2.1.  Client-Initiated Closure . . . . . . . . . . . . . . . 44
       7.2.2.  Server-Initiated Closure . . . . . . . . . . . . . . . 44
       7.2.3.  Recovering from Abnormal Closure . . . . . . . . . . . 44
     7.3.  Normal Closure of Connections  . . . . . . . . . . . . . . 45
     7.4.  Status Codes . . . . . . . . . . . . . . . . . . . . . . . 45
       7.4.1.  Defined Status Codes . . . . . . . . . . . . . . . . . 45
       7.4.2.  Reserved Status Code Ranges  . . . . . . . . . . . . . 47
   8.  Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 48
     8.1.  Handling Errors in UTF-8-Encoded Data  . . . . . . . . . . 48
   9.  Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . 48
     9.1.  Negotiating Extensions . . . . . . . . . . . . . . . . . . 48
     9.2.  Known Extensions . . . . . . . . . . . . . . . . . . . . . 50
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 50
     10.1. Non-Browser Clients  . . . . . . . . . . . . . . . . . . . 50
     10.2. Origin Considerations  . . . . . . . . . . . . . . . . . . 50
     10.3. Attacks On Infrastructure (Masking)  . . . . . . . . . . . 51
     10.4. Implementation-Specific Limits . . . . . . . . . . . . . . 52
     10.5. WebSocket Client Authentication  . . . . . . . . . . . . . 53
     10.6. Connection Confidentiality and Integrity . . . . . . . . . 53
     10.7. Handling of Invalid Data . . . . . . . . . . . . . . . . . 53
     10.8. Use of SHA-1 by the WebSocket Handshake  . . . . . . . . . 54
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 54
     11.1. Registration of New URI Schemes  . . . . . . . . . . . . . 54
       11.1.1. Registration of "ws" Scheme  . . . . . . . . . . . . . 54
       11.1.2. Registration of "wss" Scheme . . . . . . . . . . . . . 55
     11.2. Registration of the "WebSocket" HTTP Upgrade Keyword . . . 56
     11.3. Registration of New HTTP Header Fields . . . . . . . . . . 57
       11.3.1. Sec-WebSocket-Key  . . . . . . . . . . . . . . . . . .