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333 lines
10 KiB
HTML
333 lines
10 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>LuaSocket: Network support for the Lua language</title>
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<link rel="stylesheet" href="reference.css" type="text/css">
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</head>
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<body>
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<!-- header ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<div class=header>
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<hr>
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<center>
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<table summary="LuaSocket logo">
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<tr><td align=center><a href="http://www.lua.org">
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<img border=0 alt="LuaSocket" src="luasocket.png">
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</a></td></tr>
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<tr><td align=center valign=top>Network support for the Lua language
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</td></tr>
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</table>
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<p class=bar>
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<a href="home.html">home</a> ·
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<a href="home.html#download">download</a> ·
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<a href="introduction.html">introduction</a> ·
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<a href="reference.html">reference</a>
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</p>
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</center>
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<hr>
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</div>
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<!-- http +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<h2 id=http>HTTP</h2>
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<p>
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HTTP (Hyper Text Transfer Protocol) is the protocol used to exchange
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information between web-browsers and servers. The <tt>http.lua</tt>
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module offers support for the client side of the HTTP protocol (i.e.,
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the facilities that would be used by a web-browser implementation). The
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implementation conforms to the HTTP/1.1 standard,
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<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2616.txt">RFC
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2616</a>.
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</p>
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<p>
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The module exports functions that provide HTTP functionality in different
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levels of abstraction, from the simple <a
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href="#get"><tt>get</tt></a> function to the generic, LTN12 based <a
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href="#request"><tt>request</tt></a> function.
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</p>
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<p>
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URLs must conform to
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<a href="http://www.cs.princeton.edu/~diego/rfc/rfc1738.txt">RFC
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1738</a>,
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that is, an URL is a string in the form:
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</p>
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<blockquote>
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<pre>
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[http://][<user>[:<password>]@]<host>[:<port>][/<path>]
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</pre>
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</blockquote>
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<p>
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MIME headers are represented as a Lua table in the form:
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</p>
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<blockquote>
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<table summary="MIME headers in Lua table">
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<tr><td><tt>
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headers = {<br>
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field-1-name = <i>field-1-value</i>,<br>
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field-2-name = <i>field-2-value</i>,<br>
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field-3-name = <i>field-3-value</i>,
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</tt></td></tr>
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<tr><td align=center><tt>
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...
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</tt></td></tr>
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<tr><td><tt>
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field-n-name = <i>field-n-value</i><br>
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}
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</tt></td></tr>
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</table>
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</blockquote>
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<p>
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Field names are case insensitive (as specified by the standard) and all
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functions work with lowercase field names.
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Field values are left unmodified.
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</p>
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<p class=note>
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Note: MIME headers are independent of order. Therefore, there is no problem
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in representing them in a Lua table.
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</p>
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<p>
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The following constants can be set to control the default behaviour of
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the HTTP module:
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</p>
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<ul>
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<li> <tt>PORT</tt>: default port used for connections;
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<li> <tt>PROXY</tt>: default proxy used for connections;
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<li> <tt>TIMEOUT</tt>: sets the timeout for all I/O operations;
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<li> <tt>USERAGENT</tt>: default user agent reported to server.
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</ul>
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<!-- http.get +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id=get>
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http.<b>get(</b>url<b>)</b><br>
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</p>
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<p class=description>
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Performs the HTTP method <tt>GET</tt>.
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</p>
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<p class=parameters>
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<tt>Url</tt> identifies the entity to retrieve.
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</p>
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<p class=return>
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If successful, the function returns the response message body, the mime
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headers, and the status code. In case of failure, the
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function returns <tt><b>nil</b></tt> followed by an error message.
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</p>
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<p class=note>
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Note: The function is trivially implemented with the use of the
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<a href="#request"><tt>request</tt></a> function.
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</p>
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<pre class=example>
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-- load the http module
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http = require("http")
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-- connect to server "www.tecgraf.puc-rio.br" and retrieves this manual
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-- file from "/luasocket/http.html"
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b, h, c = http.get("http://www.tecgraf.puc-rio.br/luasocket/http.html")
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-- connect to server "www.tecgraf.puc-rio.br" and tries to retrieve
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-- "~diego/auth/index.html". Fails because authentication is needed.
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b, h, c = http.get("http://www.tecgraf.puc-rio.br/~diego/auth/index.html")
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-- b returns some useless page telling about the denied access,
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-- h returns authentication information
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-- and c returns with value 401 (Authentication Required)
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-- tries to connect to server "wrong.host" to retrieve "/"
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-- and fails because the host does not exist.
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r, e = http.get("http://wrong.host/")
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-- r is nil, and e returns with value "host not found"
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</pre>
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<!-- http.post ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id=post>
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http.<b>post(</b>url, body<b>)</b><br>
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</p>
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<p class=description>
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Same as <a href="#get"><tt>get</tt></a>, except
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that the <tt>POST</tt> method is used and the request
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message <tt>body</tt> is sent along with the request.
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</p>
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<p class=note>
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Note: This function is also trivially implemented with the use of the
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<a href="#request"><tt>request</tt></a> function.
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</p>
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<!-- http.request ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id=request>
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http.<b>request{</b><br>
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url = <i>string</i>,<br>
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[sink = <i>LTN12 sink</i>],]<br>
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[method = <i>string</i>,]<br>
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[headers = <i>header-table</i>,]<br>
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[source = <i>LTN12 source</i>],<br>
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[step = <i>LTN12 pump step</i>,]<br>
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[proxy = <i>string</i>,]<br>
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[redirect = <i>boolean</i>]<br>
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<b>}</b>
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</p>
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<p class=description>
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Performs the generic HTTP request, controled by a request table.
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</p>
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<p class=parameters>
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The most important parameters are the <tt>url</tt> and the <em>simple</em> LTN12 <tt>sink</tt> that will receive the downloaded content.
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Any part of the <tt>url</tt> can be overriden by including
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the appropriate field in the request table.
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If authentication information is provided, the function
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uses the Basic Authentication Scheme (see <a href="#authentication">note</a>)
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to retrieve the document. If <tt>sink</tt> is <tt><b>nil</b></tt>, the
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function discards the downloaded data. The optional parameters are the
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following:
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</p>
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<ul>
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<li><tt>method</tt>: The HTTP request method. Defaults to "GET";
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<li><tt>headers</tt>: Any additional HTTP headers to send with the request;
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<li><tt>source</tt>: <em>simple</em> LTN12 source to provide the request body. If there
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is a body, you need to provide an appropriate "<tt>content-length</tt>"
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request header field, or the function will attempt to send the body as
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"<tt>chunked</tt>" (something few servers support). Defaults to the empty source;
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<li><tt>step</tt>: LTN12 pump step function used to move data.
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Defaults to the LTN12 <tt>pump.step</tt> function.
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<li><tt>proxy</tt>: The URL of a proxy server to use. Defaults to no proxy;
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<li><tt>redirect</tt>: Set to <tt><b>false</b></tt> to prevent the
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function from automatically following 301 or 302 server redirect messages.
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</ul>
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<p class=return>
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In case of failure, the function returns <tt><b>nil</b></tt> followed by an
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error message. If successful, the function returns a table
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with all components of the response message. The response table has the following form:
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</p>
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<blockquote><tt>
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respt = {<br>
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headers = <i>header-table</i>,<br>
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status = <i>string</i>,<br>
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code = <i>number</i>,<br>
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}
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</tt></blockquote>
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<p class=return>
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Even when there was failure (URL not found, for example), the
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function usually succeeds retrieving a message body (a web page informing the
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URL was not found or some other useless page). To make sure the
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operation was successful, check the returned status <tt>code</tt>. For
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a list of the possible values and their meanings, refer to <a
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href="http://www.cs.princeton.edu/~diego/rfc/rfc2616.txt">RFC
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2616</a>.
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</p>
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<pre class=example>
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-- load the http module
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http = require("http")
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-- Requests information about a document, without downloading it.
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-- Useful, for example, if you want to display a download gauge and need
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-- to know the size of the document in advance
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respt = http.request {
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method = "HEAD",
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url = "http://www.tecgraf.puc-rio.br/~diego"
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}
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-- Would return the following headers:
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-- respt.headers = {
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-- date = "Tue, 18 Sep 2001 20:42:21 GMT",
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-- server = "Apache/1.3.12 (Unix) (Red Hat/Linux)",
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-- ["last-modified"] = "Wed, 05 Sep 2001 06:11:20 GMT",
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-- ["content-length"] = 15652,
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-- ["connection"] = "close",
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-- ["content-Type"] = "text/html"
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-- }
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</pre>
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</blockquote>
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<p class=note id=authentication>
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Note: Some URLs are protected by their
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servers from anonymous download. For those URLs, the server must receive
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some sort of authentication along with the request or it will deny
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download and return status "401 Authentication Required".
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</p>
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<p class=note>
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The HTTP/1.1 standard defines two authentication methods: the Basic
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Authentication Scheme and the Digest Authentication Scheme, both
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explained in detail in
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<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2068.txt">RFC 2068</a>.
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</p>
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<p class=note>The Basic Authentication Scheme sends
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<tt><user></tt> and
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<tt><password></tt> unencrypted to the server and is therefore
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considered unsafe. Unfortunately, by the time of this implementation,
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the wide majority of servers and browsers support the Basic Scheme only.
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Therefore, this is the method used by the toolkit whenever
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authentication is required.
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</p>
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<pre class=example>
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-- load required modules
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http = require("http")
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mime = require("mime")
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-- Connect to server "www.tecgraf.puc-rio.br" and tries to retrieve
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-- "~diego/auth/index.html", using the provided name and password to
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-- authenticate the request
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respt = http.request{
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url = "http://www.tecgraf.puc-rio.br/~diego/auth/index.html",
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user = "diego",
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password = "password"
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}
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-- Alternatively, one could fill the appropriate header and authenticate
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-- the request directly.
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respt = http.request {
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url = "http://www.tecgraf.puc-rio.br/~diego/auth/index.html",
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headers = { authentication = "Basic " .. (mime.b64("diego:password")) }
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}
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</pre>
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<!-- footer +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<div class=footer>
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<hr>
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<center>
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<p class=bar>
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<a href="home.html">home</a> ·
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<a href="home.html#download">download</a> ·
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<a href="introduction.html">introduction</a> ·
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<a href="reference.html">reference</a>
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</p>
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<p>
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<small>
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Last modified by Diego Nehab on <br>
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Sat Aug 9 01:00:41 PDT 2003
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</small>
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</p>
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</center>
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</div>
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</body>
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</html>
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