482 lines
14 KiB
HTML
482 lines
14 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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<meta name="description" content="LuaSocket: The core namespace">
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<meta name="keywords" content="Lua, LuaSocket, Socket, Network, Library, Support">
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<title>LuaSocket: The socket namespace</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="https://www.lua.org">
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<img width="128" height="128" 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="index.html">home</a> ·
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<a href="index.html#download">download</a> ·
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<a href="installation.html">installation</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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<!-- socket +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<h2 id="socket">The socket namespace</h2>
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<p>
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The <tt>socket</tt> namespace contains the core functionality of LuaSocket.
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</p>
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<p>
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To obtain the <tt>socket</tt> namespace, run:
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</p>
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<pre class="example">
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-- loads the socket module
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local socket = require("socket")
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</pre>
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<!-- headers.canonic ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="headers.canonic">
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socket.headers.<b>canonic</b></p>
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<p> The <tt>socket.headers.canonic</tt> table
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is used by the HTTP and SMTP modules to translate from
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lowercase field names back into their canonic
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capitalization. When a lowercase field name exists as a key
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in this table, the associated value is substituted in
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whenever the field name is sent out.
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</p>
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<p>
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You can obtain the <tt>headers</tt> namespace if case run-time
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modifications are required by running:
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</p>
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<pre class="example">
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-- loads the headers module
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local headers = require("headers")
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</pre>
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<!-- bind ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="bind">
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socket.<b>bind(</b>address, port [, backlog]<b>)</b>
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</p>
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<p class="description">
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This function is a shortcut that creates and returns a TCP server object
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bound to a local <tt>address</tt> and <tt>port</tt>, ready to
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accept client connections. Optionally,
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user can also specify the <tt>backlog</tt> argument to the
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<a href="tcp.html#listen"><tt>listen</tt></a> method (defaults to 32).
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</p>
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<p class="note">
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Note: The server object returned will have the option "<tt>reuseaddr</tt>"
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set to <tt><b>true</b></tt>.
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</p>
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<!-- connect ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="connect">
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socket.<b>connect[46](</b>address, port [, locaddr] [, locport] [, family]<b>)</b>
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</p>
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<p class="description">
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This function is a shortcut that creates and returns a TCP client object
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connected to a remote <tt>address</tt> at a given <tt>port</tt>. Optionally,
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the user can also specify the local address and port to bind
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(<tt>locaddr</tt> and <tt>locport</tt>), or restrict the socket family
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to "<tt>inet</tt>" or "<tt>inet6</tt>".
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Without specifying <tt>family</tt> to <tt>connect</tt>, whether a tcp or tcp6
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connection is created depends on your system configuration. Two variations
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of connect are defined as simple helper functions that restrict the
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<tt>family</tt>, <tt>socket.connect4</tt> and <tt>socket.connect6</tt>.
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</p>
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<!-- debug ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="debug">
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socket.<b>_DEBUG</b>
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</p>
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<p class="description">
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This constant is set to <tt><b>true</b></tt> if the library was compiled
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with debug support.
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</p>
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<!-- datagramsize +++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="datagramsize">
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socket.<b>_DATAGRAMSIZE</b>
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</p>
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<p class="description">
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Default datagram size used by calls to
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<a href="udp.html#receive"><tt>receive</tt></a> and
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<a href="udp.html#receivefrom"><tt>receivefrom</tt></a>.
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(Unless changed in compile time, the value is 8192.)
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</p>
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<!-- get time +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="gettime">
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socket.<b>gettime()</b>
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</p>
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<p class="description">
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Returns the UNIX time in seconds. You should subtract the values returned by this function
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to get meaningful values.
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</p>
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<pre class="example">
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t = socket.gettime()
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-- do stuff
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print(socket.gettime() - t .. " seconds elapsed")
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</pre>
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<!-- newtry +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="newtry">
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socket.<b>newtry(</b>finalizer<b>)</b>
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</p>
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<p class="description">
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Creates and returns a <em>clean</em>
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<a href="#try"><tt>try</tt></a>
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function that allows for cleanup before the exception
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is raised.
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</p>
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<p class="parameters">
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<tt>Finalizer</tt> is a function that will be called before
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<tt>try</tt> throws the exception.
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</p>
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<p class="return">
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The function returns your customized <tt>try</tt> function.
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</p>
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<p class="note">
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Note: This idea saved a <em>lot</em> of work with the
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implementation of protocols in LuaSocket:
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</p>
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<pre class="example">
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foo = socket.protect(function()
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-- connect somewhere
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local c = socket.try(socket.connect("somewhere", 42))
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-- create a try function that closes 'c' on error
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local try = socket.newtry(function() c:close() end)
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-- do everything reassured c will be closed
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try(c:send("hello there?\r\n"))
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local answer = try(c:receive())
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...
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try(c:send("good bye\r\n"))
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c:close()
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end)
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</pre>
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<!-- protect +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="protect">
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socket.<b>protect(</b>func<b>)</b>
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</p>
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<p class="description">
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Converts a function that throws exceptions into a safe function. This
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function only catches exceptions thrown by the <a href="#try"><tt>try</tt></a>
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and <a href="#newtry"><tt>newtry</tt></a> functions. It does not catch normal
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Lua errors.
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</p>
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<p class="parameters">
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<tt>Func</tt> is a function that calls
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<a href="#try"><tt>try</tt></a> (or <tt>assert</tt>, or <tt>error</tt>)
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to throw exceptions.
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</p>
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<p class="return">
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Returns an equivalent function that instead of throwing exceptions in case of
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a failed <a href="#try"><tt>try</tt></a> call, returns <tt><b>nil</b></tt>
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followed by an error message.
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</p>
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<!-- select +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="select">
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socket.<b>select(</b>recvt, sendt [, timeout]<b>)</b>
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</p>
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<p class="description">
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Waits for a number of sockets to change status.
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</p>
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<p class="parameters">
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<tt>Recvt</tt> is an array with the sockets to test for characters
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available for reading. Sockets in the <tt>sendt</tt> array are watched to
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see if it is OK to immediately write on them. <tt>Timeout</tt> is the
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maximum amount of time (in seconds) to wait for a change in status. A
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<tt><b>nil</b></tt>, negative or omitted <tt>timeout</tt> value allows the
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function to block indefinitely. <tt>Recvt</tt> and <tt>sendt</tt> can also
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be empty tables or <tt><b>nil</b></tt>. Non-socket values (or values with
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non-numeric indices) in the arrays will be silently ignored.
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</p>
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<p class="return"> The function returns a list with the sockets ready for
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reading, a list with the sockets ready for writing and an error message.
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The error message is "<tt>timeout</tt>" if a timeout
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condition was met, "<tt>select failed</tt>" if the call
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to <tt>select</tt> failed, and
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<tt><b>nil</b></tt> otherwise. The returned tables are
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doubly keyed both by integers and also by the sockets
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themselves, to simplify the test if a specific socket has
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changed status.
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</p>
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<p class="note">
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<b>Note:</b> <tt>select</tt> can monitor a limited number
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of sockets, as defined by the constant <a href="#setsize">
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<tt>socket._SETSIZE</tt></a>. This
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number may be as high as 1024 or as low as 64 by default,
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depending on the system. It is usually possible to change this
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at compile time. Invoking <tt>select</tt> with a larger
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number of sockets will raise an error.
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</p>
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<p class="note">
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<b>Important note</b>: a known bug in WinSock causes <tt>select</tt> to fail
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on non-blocking TCP sockets. The function may return a socket as
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writable even though the socket is <em>not</em> ready for sending.
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</p>
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<p class="note">
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<b>Another important note</b>: calling select with a server socket in the receive parameter before a call to accept does <em>not</em> guarantee
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<a href="tcp.html#accept"><tt>accept</tt></a> will return immediately.
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Use the <a href="tcp.html#settimeout"><tt>settimeout</tt></a>
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method or <tt>accept</tt> might block forever.
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</p>
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<p class="note">
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<b>Yet another note</b>: If you close a socket and pass
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it to <tt>select</tt>, it will be ignored.
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</p>
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<p class="note">
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<b>Using select with non-socket objects</b>: Any object that implements <tt>getfd</tt> and <tt>dirty</tt> can be used with <tt>select</tt>, allowing objects from other libraries to be used within a <tt>socket.select</tt> driven loop.
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</p>
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<!-- setsize ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="setsize">
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socket.<b>_SETSIZE</b>
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</p>
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<p class="description">
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The maximum number of sockets that the <a
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href="#select"><tt>select</tt></a> function can handle.
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</p>
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<!-- sink ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="sink">
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socket.<b>sink(</b>mode, socket<b>)</b>
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</p>
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<p class="description">
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Creates an
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<a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
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sink from a stream socket object.
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</p>
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<p class="parameters">
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<tt>Mode</tt> defines the behavior of the sink. The following
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options are available:
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</p>
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<ul>
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<li> <tt>"http-chunked"</tt>: sends data through socket after applying the
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<em>chunked transfer coding</em>, closing the socket when done;</li>
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<li> <tt>"close-when-done"</tt>: sends all received data through the
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socket, closing the socket when done;</li>
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<li> <tt>"keep-open"</tt>: sends all received data through the
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socket, leaving it open when done.</li>
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</ul>
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<p>
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<tt>Socket</tt> is the stream socket object used to send the data.
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</p>
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<p class="return">
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The function returns a sink with the appropriate behavior.
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</p>
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<!-- skip ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="skip">
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socket.<b>skip(</b>d [, ret<sub>1</sub>, ret<sub>2</sub> ... ret<sub>N</sub>]<b>)</b>
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</p>
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<p class="description">
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Drops a number of arguments and returns the remaining.
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</p>
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<p class="parameters">
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<tt>D</tt> is the number of arguments to drop. <tt>Ret<sub>1</sub></tt> to
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<tt>ret<sub>N</sub></tt> are the arguments.
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</p>
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<p class="return">
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The function returns <tt>ret<sub>d+1</sub></tt> to <tt>ret<sub>N</sub></tt>.
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</p>
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<p class="note">
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Note: This function is useful to avoid creation of dummy variables:
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</p>
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<pre class="example">
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-- get the status code and separator from SMTP server reply
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local code, sep = socket.skip(2, string.find(line, "^(%d%d%d)(.?)"))
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</pre>
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<!-- sleep ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="sleep">
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socket.<b>sleep(</b>time<b>)</b>
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</p>
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<p class="description">
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Freezes the program execution during a given amount of time.
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</p>
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<p class="parameters">
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<tt>Time</tt> is the number of seconds to sleep for. If
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<tt>time</tt> is negative, the function returns immediately.
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</p>
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<!-- source +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="source">
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socket.<b>source(</b>mode, socket [, length]<b>)</b>
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</p>
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<p class="description">
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Creates an
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<a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
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source from a stream socket object.
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</p>
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<p class="parameters">
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<tt>Mode</tt> defines the behavior of the source. The following
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options are available:
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</p>
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<ul>
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<li> <tt>"http-chunked"</tt>: receives data from socket and removes the
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<em>chunked transfer coding</em> before returning the data;</li>
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<li> <tt>"by-length"</tt>: receives a fixed number of bytes from the
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socket. This mode requires the extra argument <tt>length</tt>;</li>
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<li> <tt>"until-closed"</tt>: receives data from a socket until the other
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side closes the connection.</li>
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</ul>
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<p>
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<tt>Socket</tt> is the stream socket object used to receive the data.
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</p>
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<p class="return">
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The function returns a source with the appropriate behavior.
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</p>
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<!-- socketinvalid ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="socketinvalid">
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socket.<b>_SOCKETINVALID</b>
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</p>
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<p class="description">
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The OS value for an invalid socket. This can be used with <a href="tcp.html#getfd">
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<tt>tcp:getfd</tt></a> and <a href="tcp.html#setfd"><tt>tcp:setfd</tt></a> methods.
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</p>
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<!-- try ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="try">
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socket.<b>try(</b>ret<sub>1</sub> [, ret<sub>2</sub> ... ret<sub>N</sub>]<b>)</b>
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</p>
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<p class="description">
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Throws an exception in case <tt>ret<sub>1</sub></tt> is falsy, using
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<tt>ret<sub>2</sub></tt> as the error message. The exception is supposed to be caught
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by a <a href="#protect"><tt>protect</tt></a>ed function only.
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</p>
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<p class="parameters">
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<tt>Ret<sub>1</sub></tt> to <tt>ret<sub>N</sub></tt> can be arbitrary
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arguments, but are usually the return values of a function call
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nested with <tt>try</tt>.
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</p>
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<p class="return">
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The function returns <tt>ret</tt><sub>1</sub> to <tt>ret</tt><sub>N</sub> if
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<tt>ret</tt><sub>1</sub> is not <tt><b>nil</b></tt> or <tt><b>false</b></tt>.
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Otherwise, it calls <tt>error</tt> passing <tt>ret</tt><sub>2</sub> wrapped
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in a table with metatable used by <a href="#protect"><tt>protect</tt></a> to
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distinguish exceptions from runtime errors.
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</p>
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<pre class="example">
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-- connects or throws an exception with the appropriate error message
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c = socket.try(socket.connect("localhost", 80))
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</pre>
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<!-- version ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class="name" id="version">
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socket.<b>_VERSION</b>
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</p>
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<p class="description">
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This constant has a string describing the current LuaSocket version.
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</p>
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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="index.html">home</a> ·
|
|
<a href="index.html#down">download</a> ·
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<a href="installation.html">installation</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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Thu Apr 20 00:25:54 EDT 2006
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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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