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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: DNS support">
<meta name="keywords" content="Lua, LuaSocket, DNS, Network, Library, Support">
<title>LuaSocket: DNS 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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</center>
<hr>
</div>
<!-- dns ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<h2 id="dns">DNS</h2>
<p>
IPv4 name resolution functions
<a href="#toip"><tt>dns.toip</tt></a>
and
<a href="#tohostname"><tt>dns.tohostname</tt></a>
return <em>all</em> information obtained from
the resolver in a table of the form:
</p>
<blockquote><tt>
resolved4 = {<br>
name = <i>canonic-name</i>,<br>
alias = <i>alias-list</i>,<br>
ip = <i>ip-address-list</i><br>
}
</tt> </blockquote>
<p>
Note that the <tt>alias</tt> list can be empty.
</p>
<p>
The more general name resolution function
<a href="#getaddrinfo"><tt>dns.getaddrinfo</tt></a>, which
supports both IPv6 and IPv4,
returns <em>all</em> information obtained from
the resolver in a table of the form:
</p>
<blockquote><tt>
resolved6 = {<br>
[1] = {<br>
family = <i>family-name-1</i>,<br>
addr = <i>address-1</i><br>
},<br>
...<br>
[n] = {<br>
family = <i>family-name-n</i>,<br>
addr = <i>address-n</i><br>
}<br>
}
</tt> </blockquote>
<p>
Here, <tt>family</tt> contains the string <tt>"inet"</tt> for IPv4
addresses, and <tt>"inet6"</tt> for IPv6 addresses.
</p>
<!-- getaddrinfo ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="getaddrinfo">
socket.dns.<b>getaddrinfo(</b>address<b>)</b>
</p>
<p class="description">
Converts from host name to address.
</p>
<p class="parameters">
<tt>Address</tt> can be an IPv4 or IPv6 address or host name.
</p>
<p class="return">
The function returns a table with all information returned by
the resolver. In case of error, the function returns <b><tt>nil</tt></b>
followed by an error message.
</p>
<!-- getnameinfo ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="getnameinfo">
socket.dns.<b>getnameinfo(</b>[host] [, service]<b>)</b>
</p>
<p class="description">
Resolves a host and/or a service name through the system resolver and
returns their canonical name form. At least one of <tt>host</tt> or
<tt>service</tt> must be given.
</p>
<p class="parameters">
<tt>Host</tt> is an optional string with a host name or IP address.
<tt>Service</tt> is an optional string with a service name or port number.
</p>
<p class="return">
If <tt>host</tt> was given, returns a numerically-indexed table with the
canonical host name found for each address the resolver returns for
<tt>host</tt>. If <tt>service</tt> was also given, the canonical service
name is returned as an additional value; if only <tt>service</tt> was
given, its canonical name is returned by itself. In case of error, the
function returns <b><tt>nil</tt></b> followed by an error message.
</p>
<!-- gethostname ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="gethostname">
socket.dns.<b>gethostname()</b>
</p>
<p class="description">
Returns the standard host name for the machine as a string.
</p>
<!-- tohostname +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="tohostname">
socket.dns.<b>tohostname(</b>address<b>)</b>
</p>
<p class="description">
Converts from IPv4 address to host name.
</p>
<p class="parameters">
<tt>Address</tt> can be an IP address or host name.
</p>
<p class="return">
The function returns a string with the canonic host name of the given
<tt>address</tt>, followed by a table with all information returned by
the resolver. In case of error, the function returns <b><tt>nil</tt></b>
followed by an error message.
</p>
<!-- toip +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class="name" id="toip">
socket.dns.<b>toip(</b>address<b>)</b>
</p>
<p class="description">
Converts from host name to IPv4 address.
</p>
<p class="parameters">
<tt>Address</tt> can be an IP address or host name.
</p>
<p class="return">
Returns a string with the first IP address found for <tt>address</tt>,
followed by a table with all information returned by the resolver.
In case of error, the function returns <b><tt>nil</tt></b> followed by an error
message.
</p>
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<a href="index.html">home</a> ·
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</p>
<p>
<small>
Last modified by Diego Nehab on <br>
Thu Apr 20 00:25:07 EDT 2006
</small>
</p>
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