mirror of
https://github.com/ninenines/cowboy.git
synced 2025-07-15 04:30:25 +00:00
46 lines
1.7 KiB
Markdown
46 lines
1.7 KiB
Markdown
|
The Websocket protocol
|
||
|
|
======================
|
||
|
|
|
||
|
|
This chapter explains what Websocket is and why it is
|
||
|
|
a vital component of soft realtime Web applications.
|
||
|
|
|
||
|
|
Description
|
||
|
|
-----------
|
||
|
|
|
||
|
|
Websocket is an extension to HTTP that emulates plain TCP
|
||
|
|
connections between the client, typically a Web browser,
|
||
|
|
and the server. It uses the HTTP Upgrade mechanism to
|
||
|
|
establish the connection.
|
||
|
|
|
||
|
|
Websocket connections are asynchronous, unlike HTTP. This
|
||
|
|
means that not only can the client send frames to the server
|
||
|
|
at any time, but the server can also send frames to the client
|
||
|
|
without the client initiating anything other than the
|
||
|
|
Websocket connection itself. This allows the server to push
|
||
|
|
data to the client directly.
|
||
|
|
|
||
|
|
Websocket is an IETF standard. Cowboy supports the standard
|
||
|
|
and all drafts that were previously implemented by browsers,
|
||
|
|
excluding the initial flawed draft sometimes known as
|
||
|
|
"version 0".
|
||
|
|
|
||
|
|
Implementation
|
||
|
|
--------------
|
||
|
|
|
||
|
|
Cowboy implements Websocket as a protocol upgrade. Once the
|
||
|
|
upgrade is performed from the `init/3` callback, Cowboy
|
||
|
|
switches to Websocket. Please consult the next chapter for
|
||
|
|
more information on initiating and handling Websocket
|
||
|
|
connections.
|
||
|
|
|
||
|
|
The implementation of Websocket in Cowboy is validated using
|
||
|
|
the Autobahn test suite, which is an extensive suite of tests
|
||
|
|
covering all aspects of the protocol. Cowboy passes the
|
||
|
|
suite with 100% success, including all optional tests.
|
||
|
|
|
||
|
|
Cowboy's Websocket implementation also includes the
|
||
|
|
x-webkit-deflate-frame compression draft which is being used
|
||
|
|
by some browsers to reduce the size of data being transmitted.
|
||
|
|
Cowboy will automatically use compression as long as the
|
||
|
|
`compress` protocol option is set when starting the listener.
|