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<table summary="LuaSocket logo">
<tr><td align=center><a href="http://www.lua.org">
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<tr><td align=center valign=top>Network support for the Lua language
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<!-- http +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

<h2 id=http>HTTP</h2> 

<p>
HTTP (Hyper Text  Transfer Protocol) is the protocol  used to exchange
information  between  web-browsers and  servers.  The  <tt>http.lua</tt>
module offers  support for the client  side of the HTTP  protocol (i.e.,
the facilities that would be  used by a web-browser implementation). The
implementation    conforms     to    the    HTTP/1.1     standard,
<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2616.txt">RFC
2616</a>.
</p>

<p>
The module exports functions that provide HTTP functionality in different
levels of abstraction, from a simple <a
href="#get"><tt>get</tt></a>, to the generic, stream oriented
<a href="#request_cb"><tt>request_cb</tt></a>.
</p>

<p>
URLs must conform to
<a href="http://www.cs.princeton.edu/~diego/rfc/rfc1738.txt">RFC
1738</a>,
that is, an URL is a string in the form: 
</p>

<blockquote>
<pre>
[http://][&lt;user&gt;[:&lt;password&gt;]@]&lt;host&gt;[:&lt;port&gt;][/&lt;path&gt;] 
</pre>
</blockquote>

<p>
MIME headers are represented as a Lua table in the form:
</p>

<blockquote>
<table summary="MIME headers in Lua table">
<tr><td><tt>
headers = {<br>
&nbsp;&nbsp;field-1-name = <i>field-1-value</i>,<br>
&nbsp;&nbsp;field-2-name = <i>field-2-value</i>,<br>
&nbsp;&nbsp;field-3-name = <i>field-3-value</i>,
</tt></td></tr>
<tr><td align=center><tt>
&nbsp;&nbsp;...
</tt></td></tr>
<tr><td><tt>
&nbsp;&nbsp;field-n-name = <i>field-n-value</i><br>
}
</tt></td></tr>
</table>
</blockquote>

<p>
Field names are case insensitive (as  specified by the standard) and all
functions  work with  lowercase field names.  
Field values are left unmodified.
</p>

<p class=note>
Note: MIME headers are independent of order. Therefore, there is no problem
in representing them in a Lua table. 
</p>

<!-- http.get +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

<p class=name id=get>
socket.http.<b>get(</b>url<b>)</b><br>
socket.http.<b>get{</b><br>
&nbsp;&nbsp;url = <i>string</i>,<br>
&nbsp;&nbsp;headers = <i>header-table</i>,<br>
&nbsp;&nbsp;user = <i>string</i>,<br>
&nbsp;&nbsp;password = <i>string</i>,<br>
&nbsp;&nbsp;stay = <i>bool</i>,<br>
<b>}</b>
</p>

<p class=description>
Performs  the HTTP method <tt>GET</tt>. 
</p>

<p class=parameters>
The  function can  be
called either directly with a <tt>url</tt>  or with a <em>request table</em>. 
The use of  a request table allows  complete control over the  components of
the  request.  Values  passed explicitly  as fields of the request table
override those given by the <tt>url</tt>. For a description of the fields,
see the <a href=#request><tt>request</tt></a> function.
</p>

<p class=return>
The function  returns the response  message body, the mime  headers, the
status  code and  an  error message (if  any). In  case  of failure,  the
function returns all information it managed to gather.
</p>

<p class=note>
Note: The function is trivially implemented with the use of the 
<a href="#request"><tt>request</tt></a> function. 
</p>

<pre class=example>
-- connect to server "www.tecgraf.puc-rio.br" and retrieves this manual
-- file from "/luasocket/http.html"
b, h, c, e = socket.http.get("http://www.tecgraf.puc-rio.br/luasocket/http.html")

-- connect to server "www.tecgraf.puc-rio.br" and tries to retrieve
-- "~diego/auth/index.html". Fails because authentication is needed.
b, h, c, e = socket.http.get("http://www.tecgraf.puc-rio.br/~diego/auth/index.html")
-- b returns some useless page telling about the denied access, 
-- h returns authentication information
-- and c returns with value 401 (Authentication Required)

-- tries to connect to server "wrong.host" to retrieve "/"
-- and fails because the host does not exist.
b, h, c, e = socket.http.get("http://wrong.host/")
-- b, h, c are nil, and e returns with value "host not found"
</pre>

<!-- http.post ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

<p class=name id=post>
socket.http.<b>post(</b>url, body<b>)</b><br>
socket.http.<b>post{</b><br>
&nbsp;&nbsp; url = <i>string</i>,<br>
&nbsp;&nbsp; headers = <i>header-table</i>,<br>
&nbsp;&nbsp; body = <i>string</i>,<br>
&nbsp;&nbsp; user = <i>string</i>,<br>
&nbsp;&nbsp; password = <i>string</i>,<br>
&nbsp;&nbsp; stay = <i>bool</i>,<br>
<b>}</b>
</p>

<p class=description>
Same  as <a  href="#get"><tt>get</tt></a>,  except
that the <tt>POST</tt> method is used and the  request 
message <tt>body</tt>  is sent along with the request.
</p>

<p class=note>
Note: This function is also trivially implemented with the use of the 
<a href="#request"><tt>request</tt></a> function. 
</p>

<!-- http.request ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

<p class=name id=request>
socket.http.<b>request{</b><br>
&nbsp;&nbsp;method = <i>string</i>,<br>
&nbsp;&nbsp;url = <i>string</i>,<br>
&nbsp;&nbsp;headers = <i>header-table</i>,<br>
&nbsp;&nbsp;body = <i>string</i>,<br>
&nbsp;&nbsp;user = <i>string</i>,<br>
&nbsp;&nbsp;password = <i>string</i>,<br>
&nbsp;&nbsp;stay = <i>string</i>,<br>
<b>}</b>
</p>

<p class=description>
Performs the generic HTTP  request using.
</p>

<p class=parameters>
The request uses <tt>method</tt> on <tt>url</tt>
sending the  request <tt>headers</tt>  and request <tt>body</tt>  in the
request message. If authentication information is provided, the function
uses the  Basic Authentication Scheme (see  <a href="#authentication">note</a>)
to retrieve  the document. <tt>User</tt> and  <tt>password</tt> provided
explicitly override  those given by the  <tt>url</tt>. The <tt>stay</tt>
parameter, when set to anything  but <b><tt>nil</tt></b>, prevents the function
from automatically following 301 or 302 server redirect messages. 
</p>

<p class=return>
The function returns a table with all components of the response message
it managed to retrieve. The response table has the following form:
</p>

<blockquote><tt>
response = {<br>
&nbsp;&nbsp;body = <i>string</i>,<br>
&nbsp;&nbsp;headers = <i>header-table</i>,<br>
&nbsp;&nbsp;status = <i>string</i>,<br>
&nbsp;&nbsp;code = <i>number</i>,<br>
&nbsp;&nbsp;error = <i>string</i><br>
}
</tt></blockquote>

<p class=return>
Even  when there  was failure  (URL not  found, for  example), the
function may succeed retrieving a message body (a web page informing the
URL  was  not found  or  some  other useless  page).  To  make sure  the
operation was successful, check  the returned status <tt>code</tt>. For
a  list  of  the  possible  values  and  their  meanings,  refer  to  <a
href="http://www.cs.princeton.edu/~diego/rfc/rfc2616.txt">RFC
2616</a>. 
</p>

<pre class=example>
-- Requests information about a document, without downloading it.
-- Useful, for example, if you want to display a download gauge and need
-- to know the size of the document in advance
response = socket.http.request {
  method = "HEAD",
  url = "http://www.tecgraf.puc-rio.br/~diego"
}
-- Would return the following headers:
-- response.headers = {
--   date = "Tue, 18 Sep 2001 20:42:21 GMT",
--   server = "Apache/1.3.12 (Unix)  (Red Hat/Linux)",
--   ["last-modified"] = "Wed, 05 Sep 2001 06:11:20 GMT",
--   ["content-length"] = 15652,
--   ["connection"] = "close",
--   ["content-Type"] = "text/html"
-- }
</pre>
</blockquote>

<p class=note id=authentication> 
Note: Some URLs are protected by their
servers from anonymous download. For those URLs, the server must receive
some  sort of  authentication along  with the  request or  it will  deny
download and return status "401&nbsp;Authentication Required". 
</p>

<p class=note>
The  HTTP/1.1 standard  defines  two authentication  methods: the  Basic
Authentication  Scheme  and  the   Digest  Authentication  Scheme,  both
explained in detail in
<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2068.txt">RFC 2068</a>.
</p>

<p class=note>The Basic  Authentication   Scheme  sends   
<tt>&lt;user&gt;</tt>  and
<tt>&lt;password&gt;</tt>  unencrypted to  the server  and is  therefore
considered unsafe.  Unfortunately, by  the time of  this implementation,
the wide majority of servers and browsers support the Basic Scheme only.
Therefore,   this  is   the  method   used  by   the  toolkit   whenever
authentication is required.
</p>

<pre class=example>
-- Connect to server "www.tecgraf.puc-rio.br" and tries to retrieve
-- "~diego/auth/index.html", using the provided name and password to
-- authenticate the request
response = socket.http.request{
  url = "http://www.tecgraf.puc-rio.br/~diego/auth/index.html",
  user = "diego",
  password = "password"
}

-- Alternatively, one could fill the appropriate header and authenticate
-- the request directly.
headers = {
  authentication = "Basic " .. socket.code.base64("diego:password")
}
response = socket.http.request {
  url = "http://www.tecgraf.puc-rio.br/~diego/auth/index.html",
  headers = headers
}
</pre>

<!-- request_cb +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

<p class=name id=request_cb>
socket.http.<b>request_cb(</b>request, response<b>)</b>
</p>

<p class=description>
Performs the generic HTTP  request.
</p>

<p class=parameters>
The function receives two tables as parameters. The <tt>request</tt> table
provides information about the request: 
</p>

<blockquote><tt>
request = {<br>
&nbsp;&nbsp;method = <i>string</i>,<br>
&nbsp;&nbsp;url = <i>string</i>,<br>
&nbsp;&nbsp;headers = <i>header-table</i>,<br>
&nbsp;&nbsp;body_cb = <i>send-callback</i>,<br>
&nbsp;&nbsp;user = <i>string</i>,<br>
&nbsp;&nbsp;password = <i>string</i>,<br>
&nbsp;&nbsp;stay = <i>string</i>,<br>
}</tt>
</blockquote>

<p class=parameters>
The function uses the HTTP method specified in 
<tt>request.method</tt> on the URL <tt>request.url</tt>,
sending <tt>request.headers</tt> along with the request. The request
message  body  is sent  via the send  callback <tt>request.body_cb</tt>.
If authentication information is provided, the function    uses   the Basic
Authentication    Scheme   (see    <a href="#authentication">note</a>)  to
retrieve  the document.  <tt>Request.user</tt> and
<tt>request.password</tt>  override  those  given  by the
<tt>request.url</tt>.  The <tt>request.stay</tt>  parameter,  when set  to
anything but <b><tt>nil</tt></b>, prevents the function  from automatically
following 301 or 302 server redirect messages.  
</p>

<p class=parameters>
The <tt>response</tt> table specifies information about the desired
response:
</p>

<blockquote><tt>
response = {<br>
&nbsp;&nbsp;body_cb = <i>receive-callback</i><br>
}</tt>
</blockquote>

<p class=return>
The function  returns the same  response table  as that returned  by the
<tt>socket.http.request</tt>  function, except  the  response  message body  is
returned    to    the    receive   callback   given    by    the
<tt>response.body_cb</tt> field. 
</p>

<p class=note>
Note: For more information on callbacks, please refer to 
<a href="stream.html#stream">Streaming with callbacks</a>.
</p>

<p class=note>
Note: Method names are case <em>sensitive</em>
</p>

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<p class=bar>
<a href="home.html">home</a> &middot;
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<p>
<small>
Last modified by Diego Nehab on <br>
Sat Aug 9 01:00:41 PDT 2003
</small>
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