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404 lines
12 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="http://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="home.html">home</a> ·
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<a href="home.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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<!-- 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(</b>address, port [, locaddr, locport]<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>host</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>).
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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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<!-- 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. It will be called
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in <em>protected</em> mode.
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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,
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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: Beware that if your function performs some illegal operation that
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raises an error, the protected function will catch the error and return it
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as a string. This is because the <a href=#try><tt>try</tt></a> function
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uses errors as the mechanism to throw exceptions.
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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 table with the sockets ready for
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reading, a table with the sockets ready for writing and an error message.
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The error message is "<tt>timeout</tt>" if a timeout condition was met and
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<tt><b>nil</b></tt> otherwise. The returned tables are associative, to
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simplify the test if a specific socket has changed status.
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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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<!-- 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;
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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;
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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.
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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.
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The function truncates <tt>time</tt> down to the nearest integer.
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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;
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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>;
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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.
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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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<!-- 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 time in seconds, relative to the origin of the
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universe. 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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<!-- 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 of error. The exception can only be caught
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by the <a href=#protect><tt>protect</tt></a> function. It does not explode
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into an error message.
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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>. Otherwise, it calls <tt>error</tt> passing <tt>ret</tt><sub>2</sub>.
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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="home.html">home</a> ·
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<a href="home.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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Mon Nov 21 01:58:06 EST 2005
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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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