{ "source": "doc/api/dns.markdown", "modules": [ { "textRaw": "DNS", "name": "dns", "stability": 3, "stabilityText": "Stable", "desc": "

Use require('dns') to access this module. All methods in the dns module\nuse C-Ares except for dns.lookup which uses getaddrinfo(3) in a thread\npool. C-Ares is much faster than getaddrinfo but the system resolver is\nmore constant with how other programs operate. When a user does\nnet.connect(80, 'google.com') or http.get({ host: 'google.com' }) the\ndns.lookup method is used. Users who need to do a large number of look ups\nquickly should use the methods that go through C-Ares.\n\n

\n

Here is an example which resolves 'www.google.com' then reverse\nresolves the IP addresses which are returned.\n\n

\n
var dns = require('dns');\n\ndns.resolve4('www.google.com', function (err, addresses) {\n  if (err) throw err;\n\n  console.log('addresses: ' + JSON.stringify(addresses));\n\n  addresses.forEach(function (a) {\n    dns.reverse(a, function (err, domains) {\n      if (err) {\n        throw err;\n      }\n\n      console.log('reverse for ' + a + ': ' + JSON.stringify(domains));\n    });\n  });\n});
\n", "methods": [ { "textRaw": "dns.lookup(domain, [family], callback)", "type": "method", "name": "lookup", "desc": "

Resolves a domain (e.g. 'google.com') into the first found A (IPv4) or\nAAAA (IPv6) record.\nThe family can be the integer 4 or 6. Defaults to null that indicates\nboth Ip v4 and v6 address family.\n\n

\n

The callback has arguments (err, address, family). The address argument\nis a string representation of a IP v4 or v6 address. The family argument\nis either the integer 4 or 6 and denotes the family of address (not\nnecessarily the value initially passed to lookup).\n\n

\n

On error, err is an Error object, where err.code is the error code.\nKeep in mind that err.code will be set to 'ENOENT' not only when\nthe domain does not exist but also when the lookup fails in other ways\nsuch as no available file descriptors.\n\n\n

\n", "signatures": [ { "params": [ { "name": "domain" }, { "name": "family", "optional": true }, { "name": "callback" } ] } ] }, { "textRaw": "dns.resolve(domain, [rrtype], callback)", "type": "method", "name": "resolve", "desc": "

Resolves a domain (e.g. 'google.com') into an array of the record types\nspecified by rrtype. Valid rrtypes are 'A' (IPV4 addresses, default),\n'AAAA' (IPV6 addresses), 'MX' (mail exchange records), 'TXT' (text\nrecords), 'SRV' (SRV records), 'PTR' (used for reverse IP lookups),\n'NS' (name server records) and 'CNAME' (canonical name records).\n\n

\n

The callback has arguments (err, addresses). The type of each item\nin addresses is determined by the record type, and described in the\ndocumentation for the corresponding lookup methods below.\n\n

\n

On error, err is an Error object, where err.code is\none of the error codes listed below.\n\n\n

\n", "signatures": [ { "params": [ { "name": "domain" }, { "name": "rrtype", "optional": true }, { "name": "callback" } ] } ] }, { "textRaw": "dns.resolve4(domain, callback)", "type": "method", "name": "resolve4", "desc": "

The same as dns.resolve(), but only for IPv4 queries (A records).\naddresses is an array of IPv4 addresses (e.g.\n['74.125.79.104', '74.125.79.105', '74.125.79.106']).\n\n

\n", "signatures": [ { "params": [ { "name": "domain" }, { "name": "callback" } ] } ] }, { "textRaw": "dns.resolve6(domain, callback)", "type": "method", "name": "resolve6", "desc": "

The same as dns.resolve4() except for IPv6 queries (an AAAA query).\n\n\n

\n", "signatures": [ { "params": [ { "name": "domain" }, { "name": "callback" } ] } ] }, { "textRaw": "dns.resolveMx(domain, callback)", "type": "method", "name": "resolveMx", "desc": "

The same as dns.resolve(), but only for mail exchange queries (MX records).\n\n

\n

addresses is an array of MX records, each with a priority and an exchange\nattribute (e.g. [{'priority': 10, 'exchange': 'mx.example.com'},...]).\n\n

\n", "signatures": [ { "params": [ { "name": "domain" }, { "name": "callback" } ] } ] }, { "textRaw": "dns.resolveTxt(domain, callback)", "type": "method", "name": "resolveTxt", "desc": "

The same as dns.resolve(), but only for text queries (TXT records).\naddresses is an array of the text records available for domain (e.g.,\n['v=spf1 ip4:0.0.0.0 ~all']).\n\n

\n", "signatures": [ { "params": [ { "name": "domain" }, { "name": "callback" } ] } ] }, { "textRaw": "dns.resolveSrv(domain, callback)", "type": "method", "name": "resolveSrv", "desc": "

The same as dns.resolve(), but only for service records (SRV records).\naddresses is an array of the SRV records available for domain. Properties\nof SRV records are priority, weight, port, and name (e.g.,\n[{'priority': 10, {'weight': 5, 'port': 21223, 'name': 'service.example.com'}, ...]).\n\n

\n", "signatures": [ { "params": [ { "name": "domain" }, { "name": "callback" } ] } ] }, { "textRaw": "dns.resolveNs(domain, callback)", "type": "method", "name": "resolveNs", "desc": "

The same as dns.resolve(), but only for name server records (NS records).\naddresses is an array of the name server records available for domain\n(e.g., ['ns1.example.com', 'ns2.example.com']).\n\n

\n", "signatures": [ { "params": [ { "name": "domain" }, { "name": "callback" } ] } ] }, { "textRaw": "dns.resolveCname(domain, callback)", "type": "method", "name": "resolveCname", "desc": "

The same as dns.resolve(), but only for canonical name records (CNAME\nrecords). addresses is an array of the canonical name records available for\ndomain (e.g., ['bar.example.com']).\n\n

\n", "signatures": [ { "params": [ { "name": "domain" }, { "name": "callback" } ] } ] }, { "textRaw": "dns.reverse(ip, callback)", "type": "method", "name": "reverse", "desc": "

Reverse resolves an ip address to an array of domain names.\n\n

\n

The callback has arguments (err, domains).\n\n

\n

On error, err is an Error object, where err.code is\none of the error codes listed below.\n\n

\n", "signatures": [ { "params": [ { "name": "ip" }, { "name": "callback" } ] } ] } ], "modules": [ { "textRaw": "Error codes", "name": "error_codes", "desc": "

Each DNS query can return one of the following error codes:\n\n

\n\n", "type": "module", "displayName": "Error codes" } ], "type": "module", "displayName": "DNS" } ] }