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
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
|
<!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">
<meta name="generator" content="Hugo 0.15" />
<title>Nine Nines: Sending a response</title>
<link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'>
<link href="/css/bootstrap.min.css" rel="stylesheet">
<link href="/css/99s.css" 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="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></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>Sending a response</span></h1>
<div class="paragraph"><p>The Req object also allows you to send a response.</p></div>
<div class="paragraph"><p>You can only send one response. Any other attempt will
trigger a crash. The response may be sent in one go or
with its body streamed by chunks of arbitrary size.</p></div>
<div class="paragraph"><p>You can also set headers or the response body in advance
and Cowboy will use them when you finally do reply.</p></div>
<div class="sect1">
<h2 id="_reply">Reply</h2>
<div class="sectionbody">
<div class="paragraph"><p>You can send a reply with no particular headers or body.
Cowboy will make sure to send the mandatory headers with
the response.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:reply</span></span>(<span style="color: #993399">200</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>You can define headers to be sent with the response. Note
that header names must be lowercase. Again, Cowboy will
make sure to send the mandatory headers with the response.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:reply</span></span>(<span style="color: #993399">303</span>, [
{<span style="color: #990000"><<</span><span style="color: #FF0000">"location"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"http://ninenines.eu"</span><span style="color: #990000">>></span>}
], <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>You can override headers that Cowboy would send otherwise.
Any header set by the user will be used over the ones set
by Cowboy. For example, you can advertise yourself as a
different server.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:reply</span></span>(<span style="color: #993399">200</span>, [
{<span style="color: #990000"><<</span><span style="color: #FF0000">"server"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"yaws"</span><span style="color: #990000">>></span>}
], <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>We also saw earlier how to force close the connection by
overriding the connection header.</p></div>
<div class="paragraph"><p>Finally, you can also send a body with the response. Cowboy
will automatically set the content-length header if you do.
We recommend that you set the content-type header so the
client may know how to read the body.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:reply</span></span>(<span style="color: #993399">200</span>, [
{<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"text/plain"</span><span style="color: #990000">>></span>}
], <span style="color: #FF0000">"Hello world!"</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>Here is the same example but sending HTML this time.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:reply</span></span>(<span style="color: #993399">200</span>, [
{<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"text/html"</span><span style="color: #990000">>></span>}
], <span style="color: #FF0000">"<html><head>Hello world!</head><body><p>Hats off!</p></body></html>"</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>Note that the reply is sent immediately.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_chunked_reply">Chunked reply</h2>
<div class="sectionbody">
<div class="paragraph"><p>You can also stream the response body. First, you need to
initiate the reply by sending the response status code.
Then you can send the body in chunks of arbitrary size.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:chunked_reply</span></span>(<span style="color: #993399">200</span>, <span style="color: #009900">Req</span>),
<span style="font-weight: bold"><span style="color: #000000">cowboy_req:chunk</span></span>(<span style="color: #FF0000">"Hello..."</span>, <span style="color: #009900">Req2</span>),
<span style="font-weight: bold"><span style="color: #000000">cowboy_req:chunk</span></span>(<span style="color: #FF0000">"chunked..."</span>, <span style="color: #009900">Req2</span>),
<span style="font-weight: bold"><span style="color: #000000">cowboy_req:chunk</span></span>(<span style="color: #FF0000">"world!!"</span>, <span style="color: #009900">Req2</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>You should make sure to match on <code>ok</code> as an error may be
returned.</p></div>
<div class="paragraph"><p>While it is possible to send a chunked response without
a content-type header, it is still recommended. You can
set this header or any other just like for normal replies.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:chunked_reply</span></span>(<span style="color: #993399">200</span>, [
{<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"text/html"</span><span style="color: #990000">>></span>}
], <span style="color: #009900">Req</span>),
<span style="font-weight: bold"><span style="color: #000000">cowboy_req:chunk</span></span>(<span style="color: #FF0000">"<html><head>Hello world!</head>"</span>, <span style="color: #009900">Req2</span>),
<span style="font-weight: bold"><span style="color: #000000">cowboy_req:chunk</span></span>(<span style="color: #FF0000">"<body><p>Hats off!</p></body></html>"</span>, <span style="color: #009900">Req2</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>Note that the reply and each chunk following it are sent
immediately.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_preset_response_headers">Preset response headers</h2>
<div class="sectionbody">
<div class="paragraph"><p>You can define response headers in advance. They will be
merged into the headers given in the reply call. Headers
in the reply call override preset response headers which
override the default Cowboy headers.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:set_resp_header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"allow"</span><span style="color: #990000">>></span>, <span style="color: #FF0000">"GET"</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>You can check if a response header has already been set.
This will only check the response headers that you set,
and not the ones Cowboy will add when actually sending
the reply.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #000000">cowboy_req:has_resp_header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"allow"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>It will return <code>true</code> if the header is defined, and <code>false</code>
otherwise.</p></div>
<div class="paragraph"><p>Finally, you can also delete a preset response header if
needed. If you do, it will not be sent.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:delete_resp_header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"allow"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
</div>
</div>
<div class="sect1">
<h2 id="_preset_response_body">Preset response body</h2>
<div class="sectionbody">
<div class="paragraph"><p>You can set the response body in advance. Note that this
body will be ignored if you then choose to send a chunked
reply, or if you send a reply with an explicit body.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:set_resp_body</span></span>(<span style="color: #FF0000">"Hello world!"</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>You can also set a fun that will be called when it is time
to send the body. There are three different ways of doing
that.</p></div>
<div class="paragraph"><p>If you know the length of the body that needs to be sent,
you should specify it, as it will help clients determine
the remaining download time and allow them to inform the
user.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">F</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>) <span style="color: #990000">-></span>
<span style="color: #009900">Transport</span><span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #000000">send</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #FF0000">"Hello world!"</span>)
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
<span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:set_resp_body_fun</span></span>(<span style="color: #993399">12</span>, <span style="color: #009900">F</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>If you do not know the length of the body, you should use
a chunked response body fun instead.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">F</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">SendChunk</span>) <span style="color: #990000">-></span>
<span style="color: #009900">Body</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">lists:duplicate</span></span>(<span style="font-weight: bold"><span style="color: #000000">random:uniform</span></span>(<span style="color: #993399">1024</span>, <span style="color: #FF0000">$a</span>)),
<span style="color: #009900">SendChunk</span>(<span style="color: #009900">Body</span>)
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
<span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:set_resp_body_fun</span></span>(<span style="color: #FF6600">chunked</span>, <span style="color: #009900">F</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>Finally, you can also send data on the socket directly,
without knowing the length in advance. Cowboy may be
forced to close the connection at the end of the response
though depending on the protocol capabilities.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">F</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>) <span style="color: #990000">-></span>
<span style="color: #009900">Body</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">lists:duplicate</span></span>(<span style="font-weight: bold"><span style="color: #000000">random:uniform</span></span>(<span style="color: #993399">1024</span>, <span style="color: #FF0000">$a</span>)),
<span style="color: #009900">Transport</span><span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #000000">send</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Body</span>)
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
<span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:set_resp_body_fun</span></span>(<span style="color: #009900">F</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
</div>
</div>
<div class="sect1">
<h2 id="_sending_files">Sending files</h2>
<div class="sectionbody">
<div class="paragraph"><p>You can send files directly from disk without having to
read them. Cowboy will use the <code>sendfile</code> syscall when
possible, which means that the file is sent to the socket
directly from the kernel, which is a lot more performant
than doing it from userland.</p></div>
<div class="paragraph"><p>Again, it is recommended to set the size of the file if it
can be known in advance.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">F</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>) <span style="color: #990000">-></span>
<span style="color: #009900">Transport</span><span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #000000">sendfile</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #FF0000">"priv/styles.css"</span>)
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
<span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:set_resp_body_fun</span></span>(<span style="color: #009900">FileSize</span>, <span style="color: #009900">F</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>Please see the Ranch guide for more information about
sending files.</p></div>
</div>
</div>
</div>
<div class="span3 sidecol">
<h3>
Cowboy
2.0
User Guide
</h3>
<ul>
<li><a href="/docs/en/cowboy/2.0/guide">User Guide</a></li>
<li><a href="/docs/en/cowboy/2.0/manual">Function Reference</a></li>
</ul>
<h4 id="docs-nav">Navigation</h4>
<h4>Version select</h4>
<ul>
<li><a href="/docs/en/cowboy/1.0/guide">1.0</a></li>
<li><a href="/docs/en/cowboy/2.0/guide">2.0</a></li>
</ul>
</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 2012-2016</p>
</div>
</div>
</div>
</footer>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script src="/js/bootstrap-carousel.js"></script>
<script src="/js/bootstrap-dropdown.js"></script>
<script src="/js/custom.js"></script>
</body>
</html>
|
