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<!doctype html>
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<title>DNS Node.js v0.10.23 Manual & Documentation</title>
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<h1>Node.js v0.10.23 Manual & Documentation</h1>
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<h2>Table of Contents</h2>
<ul>
<li><a href="#dns_dns">DNS</a><ul>
<li><a href="#dns_dns_lookup_domain_family_callback">dns.lookup(domain, [family], callback)</a></li>
<li><a href="#dns_dns_resolve_domain_rrtype_callback">dns.resolve(domain, [rrtype], callback)</a></li>
<li><a href="#dns_dns_resolve4_domain_callback">dns.resolve4(domain, callback)</a></li>
<li><a href="#dns_dns_resolve6_domain_callback">dns.resolve6(domain, callback)</a></li>
<li><a href="#dns_dns_resolvemx_domain_callback">dns.resolveMx(domain, callback)</a></li>
<li><a href="#dns_dns_resolvetxt_domain_callback">dns.resolveTxt(domain, callback)</a></li>
<li><a href="#dns_dns_resolvesrv_domain_callback">dns.resolveSrv(domain, callback)</a></li>
<li><a href="#dns_dns_resolvens_domain_callback">dns.resolveNs(domain, callback)</a></li>
<li><a href="#dns_dns_resolvecname_domain_callback">dns.resolveCname(domain, callback)</a></li>
<li><a href="#dns_dns_reverse_ip_callback">dns.reverse(ip, callback)</a></li>
<li><a href="#dns_error_codes">Error codes</a></li>
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<div id="apicontent">
<h1>DNS<span><a class="mark" href="#dns_dns" id="dns_dns">#</a></span></h1>
<pre class="api_stability_3">Stability: 3 - Stable</pre><p>Use <code>require('dns')</code> to access this module. All methods in the dns module
use C-Ares except for <code>dns.lookup</code> which uses <code>getaddrinfo(3)</code> in a thread
pool. C-Ares is much faster than <code>getaddrinfo</code> but the system resolver is
more consistent with how other programs operate. When a user does
<code>net.connect(80, 'google.com')</code> or <code>http.get({ host: 'google.com' })</code> the
<code>dns.lookup</code> method is used. Users who need to do a large number of lookups
quickly should use the methods that go through C-Ares.
</p>
<p>Here is an example which resolves <code>'www.google.com'</code> then reverse
resolves the IP addresses which are returned.
</p>
<pre><code>var dns = require('dns');
dns.resolve4('www.google.com', function (err, addresses) {
if (err) throw err;
console.log('addresses: ' + JSON.stringify(addresses));
addresses.forEach(function (a) {
dns.reverse(a, function (err, domains) {
if (err) {
throw err;
}
console.log('reverse for ' + a + ': ' + JSON.stringify(domains));
});
});
});</code></pre>
<h2>dns.lookup(domain, [family], callback)<span><a class="mark" href="#dns_dns_lookup_domain_family_callback" id="dns_dns_lookup_domain_family_callback">#</a></span></h2>
<p>Resolves a domain (e.g. <code>'google.com'</code>) into the first found A (IPv4) or
AAAA (IPv6) record.
The <code>family</code> can be the integer <code>4</code> or <code>6</code>. Defaults to <code>null</code> that indicates
both Ip v4 and v6 address family.
</p>
<p>The callback has arguments <code>(err, address, family)</code>. The <code>address</code> argument
is a string representation of a IP v4 or v6 address. The <code>family</code> argument
is either the integer 4 or 6 and denotes the family of <code>address</code> (not
necessarily the value initially passed to <code>lookup</code>).
</p>
<p>On error, <code>err</code> is an <code>Error</code> object, where <code>err.code</code> is the error code.
Keep in mind that <code>err.code</code> will be set to <code>'ENOENT'</code> not only when
the domain does not exist but also when the lookup fails in other ways
such as no available file descriptors.
</p>
<h2>dns.resolve(domain, [rrtype], callback)<span><a class="mark" href="#dns_dns_resolve_domain_rrtype_callback" id="dns_dns_resolve_domain_rrtype_callback">#</a></span></h2>
<p>Resolves a domain (e.g. <code>'google.com'</code>) into an array of the record types
specified by rrtype. Valid rrtypes are <code>'A'</code> (IPV4 addresses, default),
<code>'AAAA'</code> (IPV6 addresses), <code>'MX'</code> (mail exchange records), <code>'TXT'</code> (text
records), <code>'SRV'</code> (SRV records), <code>'PTR'</code> (used for reverse IP lookups),
<code>'NS'</code> (name server records) and <code>'CNAME'</code> (canonical name records).
</p>
<p>The callback has arguments <code>(err, addresses)</code>. The type of each item
in <code>addresses</code> is determined by the record type, and described in the
documentation for the corresponding lookup methods below.
</p>
<p>On error, <code>err</code> is an <code>Error</code> object, where <code>err.code</code> is
one of the error codes listed below.
</p>
<h2>dns.resolve4(domain, callback)<span><a class="mark" href="#dns_dns_resolve4_domain_callback" id="dns_dns_resolve4_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for IPv4 queries (<code>A</code> records).
<code>addresses</code> is an array of IPv4 addresses (e.g.
<code>['74.125.79.104', '74.125.79.105', '74.125.79.106']</code>).
</p>
<h2>dns.resolve6(domain, callback)<span><a class="mark" href="#dns_dns_resolve6_domain_callback" id="dns_dns_resolve6_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve4()</code> except for IPv6 queries (an <code>AAAA</code> query).
</p>
<h2>dns.resolveMx(domain, callback)<span><a class="mark" href="#dns_dns_resolvemx_domain_callback" id="dns_dns_resolvemx_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for mail exchange queries (<code>MX</code> records).
</p>
<p><code>addresses</code> is an array of MX records, each with a priority and an exchange
attribute (e.g. <code>[{'priority': 10, 'exchange': 'mx.example.com'},...]</code>).
</p>
<h2>dns.resolveTxt(domain, callback)<span><a class="mark" href="#dns_dns_resolvetxt_domain_callback" id="dns_dns_resolvetxt_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for text queries (<code>TXT</code> records).
<code>addresses</code> is an array of the text records available for <code>domain</code> (e.g.,
<code>['v=spf1 ip4:0.0.0.0 ~all']</code>).
</p>
<h2>dns.resolveSrv(domain, callback)<span><a class="mark" href="#dns_dns_resolvesrv_domain_callback" id="dns_dns_resolvesrv_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for service records (<code>SRV</code> records).
<code>addresses</code> is an array of the SRV records available for <code>domain</code>. Properties
of SRV records are priority, weight, port, and name (e.g.,
<code>[{'priority': 10, {'weight': 5, 'port': 21223, 'name': 'service.example.com'}, ...]</code>).
</p>
<h2>dns.resolveNs(domain, callback)<span><a class="mark" href="#dns_dns_resolvens_domain_callback" id="dns_dns_resolvens_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for name server records (<code>NS</code> records).
<code>addresses</code> is an array of the name server records available for <code>domain</code>
(e.g., <code>['ns1.example.com', 'ns2.example.com']</code>).
</p>
<h2>dns.resolveCname(domain, callback)<span><a class="mark" href="#dns_dns_resolvecname_domain_callback" id="dns_dns_resolvecname_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for canonical name records (<code>CNAME</code>
records). <code>addresses</code> is an array of the canonical name records available for
<code>domain</code> (e.g., <code>['bar.example.com']</code>).
</p>
<h2>dns.reverse(ip, callback)<span><a class="mark" href="#dns_dns_reverse_ip_callback" id="dns_dns_reverse_ip_callback">#</a></span></h2>
<p>Reverse resolves an ip address to an array of domain names.
</p>
<p>The callback has arguments <code>(err, domains)</code>.
</p>
<p>On error, <code>err</code> is an <code>Error</code> object, where <code>err.code</code> is
one of the error codes listed below.
</p>
<h2>Error codes<span><a class="mark" href="#dns_error_codes" id="dns_error_codes">#</a></span></h2>
<p>Each DNS query can return one of the following error codes:
</p>
<ul>
<li><code>dns.NODATA</code>: DNS server returned answer with no data.</li>
<li><code>dns.FORMERR</code>: DNS server claims query was misformatted.</li>
<li><code>dns.SERVFAIL</code>: DNS server returned general failure.</li>
<li><code>dns.NOTFOUND</code>: Domain name not found.</li>
<li><code>dns.NOTIMP</code>: DNS server does not implement requested operation.</li>
<li><code>dns.REFUSED</code>: DNS server refused query.</li>
<li><code>dns.BADQUERY</code>: Misformatted DNS query.</li>
<li><code>dns.BADNAME</code>: Misformatted domain name.</li>
<li><code>dns.BADFAMILY</code>: Unsupported address family.</li>
<li><code>dns.BADRESP</code>: Misformatted DNS reply.</li>
<li><code>dns.CONNREFUSED</code>: Could not contact DNS servers.</li>
<li><code>dns.TIMEOUT</code>: Timeout while contacting DNS servers.</li>
<li><code>dns.EOF</code>: End of file.</li>
<li><code>dns.FILE</code>: Error reading file.</li>
<li><code>dns.NOMEM</code>: Out of memory.</li>
<li><code>dns.DESTRUCTION</code>: Channel is being destroyed.</li>
<li><code>dns.BADSTR</code>: Misformatted string.</li>
<li><code>dns.BADFLAGS</code>: Illegal flags specified.</li>
<li><code>dns.NONAME</code>: Given hostname is not numeric.</li>
<li><code>dns.BADHINTS</code>: Illegal hints flags specified.</li>
<li><code>dns.NOTINITIALIZED</code>: c-ares library initialization not yet performed.</li>
<li><code>dns.LOADIPHLPAPI</code>: Error loading iphlpapi.dll.</li>
<li><code>dns.ADDRGETNETWORKPARAMS</code>: Could not find GetNetworkParams function.</li>
<li><code>dns.CANCELLED</code>: DNS query cancelled.</li>
</ul>
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