source/texk/web2c/luatexdir/luasocket/doc/http.html

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  37 <!-- http +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
  38
  39 <h2 id="http">HTTP</h2>
  40
  41 <p>
  42 HTTP (Hyper Text  Transfer Protocol) is the protocol  used to exchange
  43 information  between  web-browsers and  servers.  The  <tt>http</tt>
  44 namespace offers  full support for the client  side of the HTTP
  45 protocol (i.e.,
  46 the facilities that would be  used by a web-browser implementation). The
  47 implementation    conforms     to    the    HTTP/1.1     standard,
  48 <a href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</a>.
  49 </p>
  50
  51 <p>
  52 The module exports functions that provide HTTP functionality in different
  53 levels of abstraction. From the simple
  54 string oriented requests, through generic
  55 <a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a> based, down to even lower-level if you bother to look through the source code.
  56 </p>
  57
  58 <p>
  59 To obtain the <tt>http</tt> namespace, run:
  60 </p>
  61
  62 <pre class=example>
  63 -- loads the HTTP module and any libraries it requires
  64 local http = require("socket.http")
  65 </pre>
  66
  67 <p>
  68 URLs must conform to
  69 <a href="http://www.ietf.org/rfc/rfc1738.txt">RFC 1738</a>,
  70 that is, an URL is a string in the form:
  71 </p>
  72
  73 <blockquote>
  74 <pre>
  75 [http://][&lt;user&gt;[:&lt;password&gt;]@]&lt;host&gt;[:&lt;port&gt;][/&lt;path&gt;]
  76 </pre>
  77 </blockquote>
  78
  79 <p>
  80 MIME headers are represented as a Lua table in the form:
  81 </p>
  82
  83 <blockquote>
  84 <table summary="MIME headers in Lua table">
  85 <tr><td><tt>
  86 headers = {<br>
  87 &nbsp;&nbsp;field-1-name = <i>field-1-value</i>,<br>
  88 &nbsp;&nbsp;field-2-name = <i>field-2-value</i>,<br>
  89 &nbsp;&nbsp;field-3-name = <i>field-3-value</i>,<br>
  90 &nbsp;&nbsp;...<br>
  91 &nbsp;&nbsp;field-n-name = <i>field-n-value</i><br>
  92 }
  93 </tt></td></tr>
  94 </table>
  95 </blockquote>
  96
  97 <p>
  98 Field names are case insensitive (as specified by the standard) and all
  99 functions work with lowercase field names (but see
 100 <a href=socket.html#headers.canonic><tt>socket.headers.canonic</tt></a>).
 101 Field values are left unmodified.
 102 </p>
 103
 104 <p class=note>
 105 Note: MIME headers are independent of order. Therefore, there is no problem
 106 in representing them in a Lua table.
 107 </p>
 108
 109 <p>
 110 The following constants can be set to control the default behavior of
 111 the HTTP module:
 112 </p>
 113
 114 <ul>
 115 <li> <tt>PORT</tt>: default port used for connections;
 116 <li> <tt>PROXY</tt>: default proxy used for connections;
 117 <li> <tt>TIMEOUT</tt>: sets the timeout for all I/O operations;
 118 <li> <tt>USERAGENT</tt>: default user agent reported to server.
 119 </ul>
 120
 121
 122 <!-- http.request ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
 123
 124 <p class=name id="request">
 125 http.<b>request(</b>url [, body]<b>)</b><br>
 126 http.<b>request{</b><br>
 127 &nbsp;&nbsp;url = <i>string</i>,<br>
 128 &nbsp;&nbsp;[sink = <i>LTN12 sink</i>,]<br>
 129 &nbsp;&nbsp;[method = <i>string</i>,]<br>
 130 &nbsp;&nbsp;[headers = <i>header-table</i>,]<br>
 131 &nbsp;&nbsp;[source = <i>LTN12 source</i>],<br>
 132 &nbsp;&nbsp;[step = <i>LTN12 pump step</i>,]<br>
 133 &nbsp;&nbsp;[proxy = <i>string</i>,]<br>
 134 &nbsp;&nbsp;[redirect = <i>boolean</i>,]<br>
 135 &nbsp;&nbsp;[create = <i>function</i>]<br>
 136 <b>}</b>
 137 </p>
 138
 139 <p class=description>
 140 The request function has two forms. The simple form downloads
 141 a URL using the <tt>GET</tt> or <tt>POST</tt> method and is based
 142 on strings. The generic form performs any HTTP method and is
 143 <a href=http://lua-users.org/wiki/FiltersSourcesAndSinks>LTN12</a> based.
 144 </p>
 145
 146 <p class=parameters>
 147 If the first argument of the <tt>request</tt> function is a string, it
 148 should be an <tt>url</tt>. In that case, if a <tt>body</tt>
 149 is provided as a string, the function will perform a <tt>POST</tt> method
 150 in the <tt>url</tt>. Otherwise, it performs a <tt>GET</tt> in the
 151 <tt>url</tt>
 152 </p>
 153
 154 <p class=parameters>
 155 If the first argument is instead a table, the most important fields are
 156 the <tt>url</tt> and the <em>simple</em>
 157 <a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
 158 <tt>sink</tt> that will receive the downloaded content.
 159 Any part of the <tt>url</tt> can be overridden by including
 160 the appropriate field in the request table.
 161 If authentication information is provided, the function
 162 uses the  Basic Authentication Scheme (see  <a href="#authentication">note</a>)
 163 to retrieve  the document. If <tt>sink</tt> is <tt><b>nil</b></tt>, the
 164 function discards the downloaded data. The optional parameters are the
 165 following:
 166 </p>
 167 <ul>
 168 <li><tt>method</tt>: The HTTP request method. Defaults to "GET";
 169 <li><tt>headers</tt>: Any additional HTTP headers to send with the request;
 170 <li><tt>source</tt>: <em>simple</em>
 171 <a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
 172 source to provide the request body. If there
 173 is a body, you need to provide an appropriate "<tt>content-length</tt>"
 174 request header field, or the function will attempt to send the body as
 175 "<tt>chunked</tt>" (something few servers support). Defaults to the empty source;
 176 <li><tt>step</tt>:
 177 <a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
 178 pump step function used to move data.
 179 Defaults to the LTN12 <tt>pump.step</tt> function.
 180 <li><tt>proxy</tt>: The URL of a proxy server to use. Defaults to no proxy;
 181 <li><tt>redirect</tt>: Set to <tt><b>false</b></tt> to prevent the
 182 function from  automatically following 301 or 302 server redirect messages;
 183 <li><tt>create</tt>: An optional function to be used instead of
 184 <a href=tcp.html#socket.tcp><tt>socket.tcp</tt></a> when the communications socket is created.
 185 </ul>
 186
 187 <p class=return>
 188 In case of failure, the function returns <tt><b>nil</b></tt> followed by an
 189 error message. If successful, the simple form returns the response
 190 body as a string, followed by the response status code, the response
 191 headers and the response status line. The generic function returns the same
 192 information, except the first return value is just the number 1 (the body
 193 goes to the <tt>sink</tt>).
 194 </p>
 195
 196 <p class=return>
 197 Even  when the server fails to provide the contents of the requested URL (URL not  found, for  example),
 198 it usually returns a message body (a web page informing the
 199 URL  was  not found  or  some  other useless  page).  To  make sure  the
 200 operation was successful, check  the returned status <tt>code</tt>. For
 201 a  list  of  the  possible  values  and  their  meanings,  refer  to  <a
 202 href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</a>.
 203 </p>
 204
 205 <p class=description>
 206 Here are a few examples with the simple interface:
 207 </p>
 208
 209 <pre class=example>
 210 -- load the http module
 211 local io = require("io")
 212 local http = require("socket.http")
 213 local ltn12 = require("ltn12")
 214
 215 -- connect to server "www.cs.princeton.edu" and retrieves this manual
 216 -- file from "~diego/professional/luasocket/http.html" and print it to stdout
 217 http.request{
 218     url = "http://www.cs.princeton.edu/~diego/professional/luasocket/http.html",
 219     sink = ltn12.sink.file(io.stdout)
 220 }
 221
 222 -- connect to server "www.example.com" and tries to retrieve
 223 -- "/private/index.html". Fails because authentication is needed.
 224 b, c, h = http.request("http://www.example.com/private/index.html")
 225 -- b returns some useless page telling about the denied access,
 226 -- h returns authentication information
 227 -- and c returns with value 401 (Authentication Required)
 228
 229 -- tries to connect to server "wrong.host" to retrieve "/"
 230 -- and fails because the host does not exist.
 231 r, e = http.request("http://wrong.host/")
 232 -- r is nil, and e returns with value "host not found"
 233 </pre>
 234
 235 <p class=description>
 236 And here is an example using the generic interface:
 237 </p>
 238
 239 <pre class=example>
 240 -- load the http module
 241 http = require("socket.http")
 242
 243 -- Requests information about a document, without downloading it.
 244 -- Useful, for example, if you want to display a download gauge and need
 245 -- to know the size of the document in advance
 246 r, c, h = http.request {
 247   method = "HEAD",
 248   url = "http://www.tecgraf.puc-rio.br/~diego"
 249 }
 250 -- r is 1, c is 200, and h would return the following headers:
 251 -- h = {
 252 --   date = "Tue, 18 Sep 2001 20:42:21 GMT",
 253 --   server = "Apache/1.3.12 (Unix)  (Red Hat/Linux)",
 254 --   ["last-modified"] = "Wed, 05 Sep 2001 06:11:20 GMT",
 255 --   ["content-length"] = 15652,
 256 --   ["connection"] = "close",
 257 --   ["content-Type"] = "text/html"
 258 -- }
 259 </pre>
 260
 261 <p class=note id="post">
 262 Note: When sending a POST request, simple interface adds a
 263 "<tt>Content-type: application/x-www-form-urlencoded</tt>"
 264 header to the request. This is the type used by
 265 HTML forms. If you need another type, use the generic
 266 interface.
 267 </p>
 268
 269 <p class=note id="authentication">
 270 Note: Some URLs are protected by their
 271 servers from anonymous download. For those URLs, the server must receive
 272 some  sort of  authentication along  with the  request or  it will  deny
 273 download and return status "401&nbsp;Authentication Required".
 274 </p>
 275
 276 <p class=note>
 277 The  HTTP/1.1 standard  defines  two authentication  methods: the  Basic
 278 Authentication  Scheme  and  the   Digest  Authentication  Scheme,  both
 279 explained in detail in
 280 <a href="http://www.ietf.org/rfc/rfc2068.txt">RFC 2068</a>.
 281 </p>
 282
 283 <p class=note>The Basic  Authentication   Scheme  sends
 284 <tt>&lt;user&gt;</tt>  and
 285 <tt>&lt;password&gt;</tt>  unencrypted to  the server  and is  therefore
 286 considered unsafe.  Unfortunately, by  the time of  this implementation,
 287 the wide majority of servers and browsers support the Basic Scheme only.
 288 Therefore,   this  is   the  method   used  by   the  toolkit   whenever
 289 authentication is required.
 290 </p>
 291
 292 <pre class=example>
 293 -- load required modules
 294 http = require("socket.http")
 295 mime = require("mime")
 296
 297 -- Connect to server "www.example.com" and tries to retrieve
 298 -- "/private/index.html", using the provided name and password to
 299 -- authenticate the request
 300 b, c, h = http.request("http://fulano:silva@www.example.com/private/index.html")
 301
 302 -- Alternatively, one could fill the appropriate header and authenticate
 303 -- the request directly.
 304 r, c = http.request {
 305   url = "http://www.example.com/private/index.html",
 306   headers = { authorization = "Basic " .. (mime.b64("fulano:silva")) }
 307 }
 308 </pre>
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 322 <p>
 323 <small>
 324 Last modified by Diego Nehab on <br>
 325 Thu Apr 20 00:25:26 EDT 2006
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