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103 lines
3.4 KiB
103 lines
3.4 KiB
14 years ago
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## DNS
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Use `require('dns')` to access this module.
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Here is an example which resolves `'www.google.com'` then reverse
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resolves the IP addresses which are returned.
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var dns = require('dns');
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dns.resolve4('www.google.com', function (err, addresses) {
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if (err) throw err;
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console.log('addresses: ' + JSON.stringify(addresses));
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addresses.forEach(function (a) {
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dns.reverse(a, function (err, domains) {
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if (err) {
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console.log('reverse for ' + a + ' failed: ' +
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err.message);
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} else {
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console.log('reverse for ' + a + ': ' +
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JSON.stringify(domains));
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}
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});
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});
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});
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### dns.lookup(domain, family=null, callback)
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Resolves a domain (e.g. `'google.com'`) into the first found A (IPv4) or
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AAAA (IPv6) record.
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The callback has arguments `(err, address, family)`. The `address` argument
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is a string representation of a IP v4 or v6 address. The `family` argument
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is either the integer 4 or 6 and denotes the family of `address` (not
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neccessarily the value initially passed to `lookup`).
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### dns.resolve(domain, rrtype='A', callback)
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Resolves a domain (e.g. `'google.com'`) into an array of the record types
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specified by rrtype. Valid rrtypes are `A` (IPV4 addresses), `AAAA` (IPV6
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addresses), `MX` (mail exchange records), `TXT` (text records), `SRV` (SRV
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records), and `PTR` (used for reverse IP lookups).
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The callback has arguments `(err, addresses)`. The type of each item
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in `addresses` is determined by the record type, and described in the
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documentation for the corresponding lookup methods below.
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On error, `err` would be an instanceof `Error` object, where `err.errno` is
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one of the error codes listed below and `err.message` is a string describing
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the error in English.
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### dns.resolve4(domain, callback)
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The same as `dns.resolve()`, but only for IPv4 queries (`A` records).
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`addresses` is an array of IPv4 addresses (e.g.
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`['74.125.79.104', '74.125.79.105', '74.125.79.106']`).
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### dns.resolve6(domain, callback)
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The same as `dns.resolve4()` except for IPv6 queries (an `AAAA` query).
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### dns.resolveMx(domain, callback)
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The same as `dns.resolve()`, but only for mail exchange queries (`MX` records).
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`addresses` is an array of MX records, each with a priority and an exchange
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attribute (e.g. `[{'priority': 10, 'exchange': 'mx.example.com'},...]`).
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### dns.resolveTxt(domain, callback)
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The same as `dns.resolve()`, but only for text queries (`TXT` records).
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`addresses` is an array of the text records available for `domain` (e.g.,
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`['v=spf1 ip4:0.0.0.0 ~all']`).
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### dns.resolveSrv(domain, callback)
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The same as `dns.resolve()`, but only for service records (`SRV` records).
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`addresses` is an array of the SRV records available for `domain`. Properties
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of SRV records are priority, weight, port, and name (e.g.,
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`[{'priority': 10, {'weight': 5, 'port': 21223, 'name': 'service.example.com'}, ...]`).
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### dns.reverse(ip, callback)
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Reverse resolves an ip address to an array of domain names.
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The callback has arguments `(err, domains)`.
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If there an an error, `err` will be non-null and an instanceof the Error
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object.
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Each DNS query can return an error code.
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- `dns.TEMPFAIL`: timeout, SERVFAIL or similar.
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- `dns.PROTOCOL`: got garbled reply.
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- `dns.NXDOMAIN`: domain does not exists.
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- `dns.NODATA`: domain exists but no data of reqd type.
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- `dns.NOMEM`: out of memory while processing.
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- `dns.BADQUERY`: the query is malformed.
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