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|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta name="description" content="LuaSocket: Unix domain socket support">
<meta name="keywords" content="Lua, LuaSocket, Socket, Unix, Domain, IPC, Library, Support">
<title>LuaSocket: Unix domain socket support</title>
<link rel="stylesheet" href="reference.css" type="text/css">
</head>
<body>
<!-- header ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<div class="header">
<hr>
<center>
<table summary="LuaSocket logo">
<tr><td align="center"><a href="http://www.lua.org">
<img width="128" height="128" border="0" alt="LuaSocket" src="luasocket.png">
</a></td></tr>
<tr><td align="center" valign="top">Network support for the Lua language
</td></tr>
</table>
<p class="bar">
<a href="index.html">home</a> ·
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</p>
</center>
<hr>
</div>
<!-- unix ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<h2 id="unix">Unix domain sockets</h2>
<p>
Unix domain sockets provide inter-process communication between processes
on the same host, addressed by a path in the file system rather than by an
IP address and port. LuaSocket supports both the stream (connection
oriented, like TCP) and datagram (connectionless, like UDP) flavors.
</p>
<p class="note">
Note: This module is only built on Unix-like platforms (Linux, macOS,
BSD, Haiku). It is not available on Windows.
</p>
<p>
Unlike the core <tt>socket</tt> namespace, Unix domain socket support is a
separate module that must be required explicitly:
</p>
<pre class="example">
-- loads the socket.unix module
local unix = require("socket.unix")
</pre>
<p>
The module table returned by <tt>require("socket.unix")</tt> exposes two
constructors, <a href="#socket.unix.stream"><tt>unix.stream()</tt></a> and
<a href="#socket.unix.dgram"><tt>unix.dgram()</tt></a>. For backwards
compatibility, <tt>unix.tcp</tt> and <tt>unix.udp</tt> are aliases for
<tt>stream</tt> and <tt>dgram</tt> respectively, and the module table
itself can be called directly as a shortcut for <tt>unix.stream()</tt>
(i.e. <tt>unix()</tt> is the same as <tt>unix.stream()</tt>).
</p>
<p class="note">
Note: Paths passed to <a href="#stream.bind"><tt>bind</tt></a>,
<a href="#stream.connect"><tt>connect</tt></a> and their datagram
equivalents are limited by the platform's <tt>sun_path</tt> buffer size
(commonly around 100–108 bytes). A path that does not fit returns
<b><tt>nil</tt></b> followed by the error message '<tt>path too
long</tt>'.
</p>
<!-- stream ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<h3 id="stream">Stream (<tt>socket.unix.stream</tt>)</h3>
<p>
Stream Unix domain sockets behave like TCP sockets (see
<a href="tcp.html">TCP</a>): a freshly created object is a <em>master</em>
object, which becomes a <em>client</em> object after a successful
<a href="#stream.connect"><tt>connect</tt></a>, or a <em>server</em>
object after a successful <a href="#stream.listen"><tt>listen</tt></a>
(itself normally preceded by <a href="#stream.bind"><tt>bind</tt></a>).
Server objects produce client objects via
<a href="#stream.accept"><tt>accept</tt></a>. Most methods below work the
same way as their TCP counterparts, just addressed by path instead of
IP/port.
</p>
<!-- stream.accept ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.accept">
server:<b>accept()</b>
</p>
<p class="description">
Waits for a remote connection on the server object and returns a client
object representing that connection. Works exactly like
<a href="tcp.html#accept"><tt>tcp:accept</tt></a>.
</p>
<p class="return">
If a connection is successfully accepted, a client object is returned. If a
timeout condition is met, the method returns <b><tt>nil</tt></b> followed
by the error string '<tt>timeout</tt>'. Other errors are reported by
<b><tt>nil</tt></b> followed by a message describing the error.
</p>
<!-- stream.bind ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.bind">
master:<b>bind(</b>path<b>)</b><br>
master:<b>setsockname(</b>path<b>)</b>
</p>
<p class="description">
Binds a master object to a file system <tt>path</tt>. <tt>setsockname</tt>
is an alias for <tt>bind</tt>.
</p>
<p class="parameters">
<tt>Path</tt> is a string with the file system path to bind to. The path
must not already exist as a socket file — remove any stale socket
file left over from a previous run before binding.
</p>
<p class="return">
In case of success, the method returns 1. In case of error, the method
returns <b><tt>nil</tt></b> followed by an error message.
</p>
<!-- stream.close +++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.close">
master:<b>close()</b><br>
client:<b>close()</b><br>
server:<b>close()</b>
</p>
<p class="description">
Closes a stream Unix domain object. The internal socket used by the object
is closed. No further operations (except further calls to
<tt>close</tt>) are allowed on a closed socket.
</p>
<p class="note">
Note: Closing a socket does not remove the bound path from the file
system. Delete the socket file yourself (e.g. <tt>os.remove(path)</tt>)
once the server is done with it.
</p>
<p class="note">
Note: Garbage-collected objects are automatically closed before
destruction.
</p>
<!-- stream.connect +++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.connect">
master:<b>connect(</b>path<b>)</b><br>
master:<b>setpeername(</b>path<b>)</b>
</p>
<p class="description">
Attempts to connect a master object to <tt>path</tt>, transforming it
into a client object. <tt>setpeername</tt> is an alias for
<tt>connect</tt>. Client objects support
<a href="#stream.send"><tt>send</tt></a>,
<a href="#stream.receive"><tt>receive</tt></a>,
<a href="#stream.getsockname"><tt>getsockname</tt></a>,
<a href="#stream.settimeout"><tt>settimeout</tt></a>,
<a href="#stream.shutdown"><tt>shutdown</tt></a>, and
<a href="#stream.close"><tt>close</tt></a>.
</p>
<p class="parameters">
<tt>Path</tt> is a string with the file system path of a listening server
object.
</p>
<p class="return">
In case of error, the method returns <b><tt>nil</tt></b> followed by a
string describing the error. In case of success, the method returns 1.
</p>
<!-- stream.dirty +++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.dirty">
master:<b>dirty()</b><br>
client:<b>dirty()</b><br>
server:<b>dirty()</b>
</p>
<p class="description">
Check the read buffer status.
</p>
<p class="return">
Returns <tt>true</tt> if there is any data in the read buffer,
<tt>false</tt> otherwise.
</p>
<p class="note">
Note: <b>This is an internal method, use at your own risk.</b>
</p>
<!-- stream.getfd ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.getfd">
master:<b>getfd()</b><br>
client:<b>getfd()</b><br>
server:<b>getfd()</b>
</p>
<p class="description">
Returns the underlying socket descriptor or handle associated to the
object.
</p>
<p class="return">
The descriptor or handle.
</p>
<p class="note">
Note: <b>This is an internal method. Unlikely to be portable. Use at your
own risk.</b>
</p>
<!-- stream.getsockname +++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.getsockname">
master:<b>getsockname()</b><br>
client:<b>getsockname()</b><br>
server:<b>getsockname()</b>
</p>
<p class="description">
Returns the local path the object is bound to.
</p>
<p class="return">
The method returns a string with the local path. In case of error, the
method returns <b><tt>nil</tt></b>.
</p>
<!-- stream.getstats +++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.getstats">
master:<b>getstats()</b><br>
client:<b>getstats()</b><br>
server:<b>getstats()</b>
</p>
<p class="description">
Returns accounting information on the socket, useful for throttling of
bandwidth. Works exactly like <a href="tcp.html#getstats"><tt>tcp:getstats</tt></a>.
</p>
<p class="return">
The method returns the number of bytes received, the number of bytes
sent, and the age of the socket object in seconds.
</p>
<!-- stream.listen ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.listen">
master:<b>listen(</b>[backlog]<b>)</b>
</p>
<p class="description">
Specifies the socket is willing to receive connections, transforming the
object into a server object. Server objects support
<a href="#stream.accept"><tt>accept</tt></a>,
<a href="#stream.getsockname"><tt>getsockname</tt></a>,
<a href="#stream.setoption"><tt>setoption</tt></a>,
<a href="#stream.settimeout"><tt>settimeout</tt></a>, and
<a href="#stream.close"><tt>close</tt></a>.
</p>
<p class="parameters">
The optional <tt>backlog</tt> parameter specifies the number of client
connections that can be queued waiting for service. Defaults to 32.
</p>
<p class="return">
In case of success, the method returns 1. In case of error, the method
returns <b><tt>nil</tt></b> followed by an error message.
</p>
<!-- stream.receive +++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.receive">
client:<b>receive(</b>[pattern [, prefix [, maxsize]]]<b>)</b>
</p>
<p class="description">
Reads data from a client object. Works exactly like
<a href="tcp.html#receive"><tt>tcp:receive</tt></a>, including the
<tt>*a</tt>/<tt>*l</tt>/<tt>number</tt> patterns and the
<tt>prefix</tt>/<tt>maxsize</tt> parameters.
</p>
<!-- stream.send +++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.send">
client:<b>send(</b>data [, i [, j]]<b>)</b>
</p>
<p class="description">
Sends <tt>data</tt> through a client object. Works exactly like
<a href="tcp.html#send"><tt>tcp:send</tt></a>, including the optional
<tt>i</tt>/<tt>j</tt> substring selection.
</p>
<!-- stream.setfd ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.setfd">
master:<b>setfd(</b>fd<b>)</b><br>
client:<b>setfd(</b>fd<b>)</b><br>
server:<b>setfd(</b>fd<b>)</b>
</p>
<p class="description">
Sets the underlying socket descriptor or handle associated to the object.
The current one is simply replaced, not closed, and no other change to
the object state is made.
</p>
<p class="return">
No return value.
</p>
<p class="note">
Note: <b>This is an internal method. Unlikely to be portable. Use at your
own risk.</b>
</p>
<!-- stream.setoption +++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.setoption">
client:<b>setoption(</b>option [, value]<b>)</b><br>
server:<b>setoption(</b>option [, value]<b>)</b>
</p>
<p class="description">
Sets options for the stream object. Options are only needed by low-level
or time-critical applications. You should only modify an option if you
are sure you need it.
</p>
<p class="parameters">
<tt>Option</tt> is a string with the option name, and <tt>value</tt>
depends on the option being set:
</p>
<ul>
<li> '<tt>keepalive</tt>': Setting this option to <tt>true</tt> enables
the periodic transmission of messages on a connected socket. See
<a href="tcp.html#setoption"><tt>tcp:setoption</tt></a> for details;</li>
<li> '<tt>reuseaddr</tt>': Setting this option indicates that the rules
used in validating addresses supplied in a call to
<a href="#stream.bind"><tt>bind</tt></a> should allow reuse of local
addresses;</li>
<li> '<tt>linger</tt>': Controls the action taken when unsent data are
queued on a socket and a close is performed. See
<a href="tcp.html#setoption"><tt>tcp:setoption</tt></a> for the full
description of the <tt>on</tt>/<tt>timeout</tt> value table.</li>
</ul>
<p class="return">
The method returns 1 in case of success, or <b><tt>nil</tt></b> followed
by an error message otherwise.
</p>
<!-- stream.setstats +++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.setstats">
master:<b>setstats(</b>received, sent, age<b>)</b><br>
client:<b>setstats(</b>received, sent, age<b>)</b><br>
server:<b>setstats(</b>received, sent, age<b>)</b>
</p>
<p class="description">
Resets accounting information on the socket, useful for throttling of
bandwidth. Works exactly like
<a href="tcp.html#setstats"><tt>tcp:setstats</tt></a>.
</p>
<p class="return">
The method returns 1 in case of success and <tt><b>nil</b></tt> otherwise.
</p>
<!-- stream.settimeout +++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.settimeout">
master:<b>settimeout(</b>value [, mode]<b>)</b><br>
client:<b>settimeout(</b>value [, mode]<b>)</b><br>
server:<b>settimeout(</b>value [, mode]<b>)</b>
</p>
<p class="description">
Changes the timeout values for the object. Works exactly like
<a href="tcp.html#settimeout"><tt>tcp:settimeout</tt></a>, including the
'<tt>b</tt>' (block) and '<tt>t</tt>' (total) modes.
</p>
<!-- stream.shutdown ++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="stream.shutdown">
client:<b>shutdown(</b>[mode]<b>)</b>
</p>
<p class="description">
Shuts down part of a full-duplex connection. Works exactly like
<a href="tcp.html#shutdown"><tt>tcp:shutdown</tt></a>.
</p>
<p class="parameters">
<tt>Mode</tt> can be "<tt>both</tt>" (default), "<tt>send</tt>" or
"<tt>receive</tt>".
</p>
<p class="return">
This function returns 1.
</p>
<!-- socket.unix.stream +++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="socket.unix.stream">
unix.<b>stream()</b>
</p>
<p class="description">
Creates and returns a stream Unix domain master object. A master object
can be transformed into a server object with
<a href="#stream.listen"><tt>listen</tt></a> (after a call to
<a href="#stream.bind"><tt>bind</tt></a>) or into a client object with
<a href="#stream.connect"><tt>connect</tt></a>. The only other method
supported by a master object is <a href="#stream.close"><tt>close</tt></a>.
</p>
<p class="return">
In case of success, a new master object is returned. In case of error,
<b><tt>nil</tt></b> is returned, followed by an error message.
</p>
<!-- dgram +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<h3 id="dgram">Datagram (<tt>socket.unix.dgram</tt>)</h3>
<p>
Datagram Unix domain sockets behave like UDP sockets (see
<a href="udp.html">UDP</a>): a socket starts out unconnected, and can
optionally be turned into a connected socket with
<a href="#dgram.connect"><tt>connect</tt></a> for repeated exchanges with
a single peer.
</p>
<!-- dgram.bind +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.bind">
unconnected:<b>bind(</b>path<b>)</b><br>
unconnected:<b>setsockname(</b>path<b>)</b>
</p>
<p class="description">
Binds the datagram object to a local file system <tt>path</tt>.
<tt>setsockname</tt> is an alias for <tt>bind</tt>. Binding is only
required if you want other processes to be able to
<a href="#dgram.sendto"><tt>sendto</tt></a> this object; it is not
required to <a href="#dgram.sendto"><tt>sendto</tt></a> or
<a href="#dgram.connect"><tt>connect</tt></a> from it.
</p>
<p class="return">
In case of success, the method returns 1. In case of error, the method
returns <b><tt>nil</tt></b> followed by an error message.
</p>
<!-- dgram.close ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.close">
connected:<b>close()</b><br>
unconnected:<b>close()</b>
</p>
<p class="description">
Closes a datagram Unix domain object.
</p>
<p class="note">
Note: Closing a socket does not remove the bound path from the file
system. Delete the socket file yourself (e.g. <tt>os.remove(path)</tt>)
once you are done with it.
</p>
<p class="note">
Note: Garbage-collected objects are automatically closed before
destruction.
</p>
<!-- dgram.connect ++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.connect">
connected:<b>connect(</b>path<b>)</b><br>
unconnected:<b>connect(</b>path<b>)</b><br>
connected:<b>setpeername(</b>path<b>)</b><br>
unconnected:<b>setpeername(</b>path<b>)</b>
</p>
<p class="description">
Sets (or changes) the peer of a datagram object, turning an unconnected
object into a connected one. <tt>setpeername</tt> is an alias for
<tt>connect</tt>.
</p>
<p class="parameters">
<tt>Path</tt> is a string with the file system path of the peer.
</p>
<p class="return">
In case of error, the method returns <b><tt>nil</tt></b> followed by an
error message. In case of success, the method returns 1.
</p>
<p class="note">
Note: Unlike <a href="udp.html#setpeername"><tt>udp:setpeername</tt></a>,
there is no '<tt>*</tt>' path to dissolve the peer association back to an
unconnected socket.
</p>
<!-- dgram.dirty ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.dirty">
connected:<b>dirty()</b><br>
unconnected:<b>dirty()</b>
</p>
<p class="description">
Check the read buffer status.
</p>
<p class="return">
Always returns <tt>false</tt>. Datagram objects do not keep a read
buffer.
</p>
<p class="note">
Note: <b>This is an internal method, use at your own risk.</b>
</p>
<!-- dgram.getfd ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.getfd">
connected:<b>getfd()</b><br>
unconnected:<b>getfd()</b>
</p>
<p class="description">
Returns the underlying socket descriptor or handle associated to the
object.
</p>
<p class="return">
The descriptor or handle.
</p>
<p class="note">
Note: <b>This is an internal method. Unlikely to be portable. Use at your
own risk.</b>
</p>
<!-- dgram.getsockname +++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.getsockname">
connected:<b>getsockname()</b><br>
unconnected:<b>getsockname()</b>
</p>
<p class="description">
Returns the local path the object is bound to.
</p>
<p class="return">
The method returns a string with the local path. In case of error, the
method returns <b><tt>nil</tt></b>.
</p>
<!-- dgram.gettimeout +++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.gettimeout">
connected:<b>gettimeout()</b><br>
unconnected:<b>gettimeout()</b>
</p>
<p class="description">
Returns the current timeout value.
</p>
<!-- dgram.receive +++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.receive">
connected:<b>receive(</b>[size]<b>)</b><br>
unconnected:<b>receive(</b>[size]<b>)</b>
</p>
<p class="description">
Receives a datagram from the object. If the object is connected, only
datagrams coming from the peer are accepted.
</p>
<p class="parameters">
The optional <tt>size</tt> parameter specifies the maximum size of the
datagram to be retrieved (defaults to 8192 bytes).
</p>
<p class="return">
In case of success, the method returns the received datagram, which may
be the empty string (a valid zero-length datagram, not end-of-stream). In
case of timeout, the method returns <b><tt>nil</tt></b> followed by the
string '<tt>timeout</tt>'.
</p>
<!-- dgram.receivefrom +++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.receivefrom">
unconnected:<b>receivefrom(</b>[size]<b>)</b>
</p>
<p class="description">
Works exactly as <a href="#dgram.receive"><tt>receive</tt></a>, except it
also returns the sender's path as a second return value.
</p>
<p class="return">
In case of success, the method returns the received datagram followed by
the sender's path (the empty string if the sender's socket was not
bound). In case of timeout, the method returns <b><tt>nil</tt></b>
followed by the string '<tt>timeout</tt>'.
</p>
<!-- dgram.send +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.send">
connected:<b>send(</b>datagram<b>)</b>
</p>
<p class="description">
Sends a datagram to the peer of a connected object.
</p>
<p class="return">
If successful, the method returns the number of bytes sent. In case of
error, the method returns <b><tt>nil</tt></b> followed by an error
message (the string '<tt>refused</tt>' if the peer's socket is not
accepting datagrams).
</p>
<!-- dgram.sendto +++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.sendto">
unconnected:<b>sendto(</b>datagram, path<b>)</b>
</p>
<p class="description">
Sends a datagram to the object bound to <tt>path</tt>.
</p>
<p class="parameters">
<tt>Datagram</tt> is a string with the datagram contents. <tt>Path</tt>
is the file system path of the recipient.
</p>
<p class="return">
If successful, the method returns the number of bytes sent. In case of
error, the method returns <b><tt>nil</tt></b> followed by an error
message (the string '<tt>refused</tt>' if the recipient's socket is not
accepting datagrams).
</p>
<!-- dgram.setfd ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.setfd">
connected:<b>setfd(</b>fd<b>)</b><br>
unconnected:<b>setfd(</b>fd<b>)</b>
</p>
<p class="description">
Sets the underlying socket descriptor or handle associated to the object.
</p>
<p class="return">
No return value.
</p>
<p class="note">
Note: <b>This is an internal method. Unlikely to be portable. Use at your
own risk.</b>
</p>
<!-- dgram.setoption +++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.setoption">
connected:<b>setoption(</b>option [, value]<b>)</b><br>
unconnected:<b>setoption(</b>option [, value]<b>)</b>
</p>
<p class="description">
Sets options for the datagram object.
</p>
<p class="parameters">
<tt>Option</tt> is a string with the option name:
</p>
<ul>
<li> '<tt>reuseaddr</tt>': Indicates that the rules used in validating
addresses supplied in a <a href="#dgram.bind"><tt>bind</tt></a> call
should allow reuse of local addresses. Receives a boolean value.</li>
</ul>
<p class="return">
The method returns 1 in case of success, or <b><tt>nil</tt></b> followed
by an error message otherwise.
</p>
<!-- dgram.settimeout +++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="dgram.settimeout">
connected:<b>settimeout(</b>value<b>)</b><br>
unconnected:<b>settimeout(</b>value<b>)</b>
</p>
<p class="description">
Changes the timeout value for the object. Works like
<a href="udp.html#settimeout"><tt>udp:settimeout</tt></a>: since
<a href="#dgram.send"><tt>send</tt></a> and
<a href="#dgram.sendto"><tt>sendto</tt></a> never block, this only
affects <a href="#dgram.receive"><tt>receive</tt></a> and
<a href="#dgram.receivefrom"><tt>receivefrom</tt></a>.
</p>
<!-- socket.unix.dgram +++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="socket.unix.dgram">
unix.<b>dgram()</b>
</p>
<p class="description">
Creates and returns an unconnected datagram Unix domain object.
Unconnected objects support
<a href="#dgram.sendto"><tt>sendto</tt></a>,
<a href="#dgram.receive"><tt>receive</tt></a>,
<a href="#dgram.receivefrom"><tt>receivefrom</tt></a>,
<a href="#dgram.getsockname"><tt>getsockname</tt></a>,
<a href="#dgram.setoption"><tt>setoption</tt></a>,
<a href="#dgram.settimeout"><tt>settimeout</tt></a>,
<a href="#dgram.connect"><tt>connect</tt></a>, and
<a href="#dgram.close"><tt>close</tt></a>. Use
<a href="#dgram.connect"><tt>connect</tt></a> to turn the object into a
connected object.
</p>
<p class="return">
In case of success, a new unconnected datagram object is returned. In
case of error, <b><tt>nil</tt></b> is returned, followed by an error
message.
</p>
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