1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="">
<meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara">
<title>Nine Nines: The Websocket protocol</title>
<link href='https://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'>
<link href="/css/99s.css?r=7" rel="stylesheet">
<link rel="shortcut icon" href="/img/ico/favicon.ico">
<link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png">
<link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png">
<link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png">
</head>
<body class="">
<header id="page-head">
<div id="topbar" class="container">
<div class="row">
<div class="span2">
<h1 id="logo"><a href="/" title="99s">99s</a></h1>
</div>
<div class="span10">
<div id="side-header">
<nav>
<ul>
<li><a title="Hear my thoughts" href="/articles">Articles</a></li>
<li><a title="Watch my talks" href="/talks">Talks</a></li>
<li class="active"><a title="Read the docs" href="/docs">Documentation</a></li>
<li><a title="Request my services" href="/services">Consulting & Training</a></li>
</ul>
</nav>
<ul id="social">
<li>
<a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a>
</li>
<li>
<a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a>
</li>
</ul>
</div>
</div>
</div>
</div>
</header>
<div id="contents" class="two_col">
<div class="container">
<div class="row">
<div id="docs" class="span9 maincol">
<h1 class="lined-header"><span>The Websocket protocol</span></h1>
<p>This chapter explains what Websocket is and why it is a vital component of soft realtime Web applications.</p>
<h2 id="_description">Description</h2>
<p>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.</p>
<p>Websocket connections are fully asynchronous, unlike HTTP/1.1 (synchronous) and HTTP/2 (asynchronous, but the server can only initiate streams in response to requests). With Websocket, the client and the server can both send frames at any time without any restriction. It is closer to TCP than any of the HTTP protocols.</p>
<p>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".</p>
<h2 id="_websocket_vs_http_2">Websocket vs HTTP/2</h2>
<p>For a few years Websocket was the only way to have a bidirectional asynchronous connection with the server. This changed when HTTP/2 was introduced. While HTTP/2 requires the client to first perform a request before the server can push data, this is only a minor restriction as the client can do so just as it connects.</p>
<p>Websocket was designed as a kind-of-TCP channel to a server. It only defines the framing and connection management and lets the developer implement a protocol on top of it. For example you could implement IRC over Websocket and use a Javascript IRC client to speak to the server.</p>
<p>HTTP/2 on the other hand is just an improvement over the HTTP/1.1 connection and request/response mechanism. It has the same semantics as HTTP/1.1.</p>
<p>If all you need is to access an HTTP API, then HTTP/2 should be your first choice. On the other hand, if what you need is a different protocol, then you can use Websocket to implement it.</p>
<h2 id="_implementation">Implementation</h2>
<p>Cowboy implements Websocket as a protocol upgrade. Once the upgrade is performed from the <code>init/2</code> callback, Cowboy switches to Websocket. Please consult the next chapter for more information on initiating and handling Websocket connections.</p>
<p>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.</p>
<p>Cowboy's Websocket implementation also includes the permessage-deflate and x-webkit-deflate-frame compression extensions.</p>
<p>Cowboy will automatically use compression when the <code>compress</code> option is returned from the <code>init/2</code> function.</p>
<nav style="margin:1em 0">
<a style="float:left" href="https://ninenines.eu/docs/en/cowboy/2.7/guide/resource_design/">
Designing a resource handler
</a>
<a style="float:right" href="https://ninenines.eu/docs/en/cowboy/2.7/guide/ws_handlers/">
Websocket handlers
</a>
</nav>
</div>
<div class="span3 sidecol">
<h3>
Cowboy
2.7
User Guide
</h3>
<ul>
<li><a href="/docs/en/cowboy/2.7/guide">User Guide</a></li>
<li><a href="/docs/en/cowboy/2.7/manual">Function Reference</a></li>
</ul>
<h4 id="docs-nav">Navigation</h4>
<h4>Version select</h4>
<ul>
<li><a href="/docs/en/cowboy/2.9/guide">2.9</a></li>
<li><a href="/docs/en/cowboy/2.8/guide">2.8</a></li>
<li><a href="/docs/en/cowboy/2.7/guide">2.7</a></li>
<li><a href="/docs/en/cowboy/2.6/guide">2.6</a></li>
<li><a href="/docs/en/cowboy/2.5/guide">2.5</a></li>
<li><a href="/docs/en/cowboy/2.4/guide">2.4</a></li>
</ul>
<h3 id="_like_my_work__donate">Like my work? Donate!</h3>
<p>Donate to Loïc Hoguin because his work on Cowboy, Ranch, Gun and Erlang.mk is fantastic:</p>
<form action="https://www.paypal.com/cgi-bin/webscr" method="post" style="display:inline">
<input type="hidden" name="cmd" value="_donations">
<input type="hidden" name="business" value="[email protected]">
<input type="hidden" name="lc" value="FR">
<input type="hidden" name="item_name" value="Loic Hoguin">
<input type="hidden" name="item_number" value="99s">
<input type="hidden" name="currency_code" value="EUR">
<input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHosted">
<input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<img alt="" border="0" src="https://www.paypalobjects.com/fr_FR/i/scr/pixel.gif" width="1" height="1">
</form><p>Recurring payment options are also available via <a href="https://github.com/sponsors/essen">GitHub Sponsors</a>. These funds are used to cover the recurring expenses like food, dedicated servers or domain names.</p>
</div>
</div>
</div>
</div>
<footer>
<div class="container">
<div class="row">
<div class="span6">
<p id="scroll-top"><a href="#">↑ Scroll to top</a></p>
<nav>
<ul>
<li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li>
</ul>
</nav>
</div>
<div class="span6 credits">
<p><img src="/img/footer_logo.png"></p>
<p>Copyright © Loïc Hoguin 2012-2018</p>
</div>
</div>
</div>
</footer>
<script src="/js/custom.js"></script>
</body>
</html>
|
