node-api-dns.txt

*node-api-dns.txt*      For Node.js module `DNS` version v3.3.0.

Node.js Documentation
https://nodejs.org

==============================================================================
CONTENTS                                                   *node-api-contents*

  1. Intro                                                      |node-api-dns|
  2. Methods                                            |node-api-dns-methods|
    2.1. dns.lookup(hostname[, options], callback)     |node-api-dns.lookup()|
    2.2. dns.lookupService(address, port, callback)  |node-api-dns.lookupService()|
    2.3. dns.resolve(hostname[, rrtype], callback)    |node-api-dns.resolve()|
    2.4. dns.resolve4(hostname, callback)            |node-api-dns.resolve4()|
    2.5. dns.resolve6(hostname, callback)            |node-api-dns.resolve6()|
    2.6. dns.resolveMx(hostname, callback)          |node-api-dns.resolveMx()|
    2.7. dns.resolveTxt(hostname, callback)        |node-api-dns.resolveTxt()|
    2.8. dns.resolveSrv(hostname, callback)        |node-api-dns.resolveSrv()|
    2.9. dns.resolveSoa(hostname, callback)        |node-api-dns.resolveSoa()|
    2.10. dns.resolveNs(hostname, callback)         |node-api-dns.resolveNs()|
    2.11. dns.resolveCname(hostname, callback)   |node-api-dns.resolveCname()|
    2.12. dns.reverse(ip, callback)                   |node-api-dns.reverse()|
    2.13. dns.getServers()                         |node-api-dns.getServers()|
    2.14. dns.setServers(servers)                  |node-api-dns.setServers()|
  3. Properties                                      |node-api-dns-properties|

==============================================================================
INTRO                                                           *node-api-dns*

Stability: 2 - Stable

Use `require('dns')` to access this module.

This module contains functions that belong to two different categories:

1) Functions that use the underlying operating system facilities to perform
name resolution, and that do not necessarily do any network communication.
This category contains only one function: `dns.lookup`. **Developers looking
to perform name resolution in the same way that other applications on the same
operating system behave should use `dns.lookup`.**

Here is an example that does a lookup of `www.google.com`.

 >
  var dns = require('dns');
  
  dns.lookup('www.google.com', function onLookup(err, addresses, family) {
    console.log('addresses:', addresses);
  });
<

2) Functions that connect to an actual DNS server to perform name resolution,
and that __always__ use the network to perform DNS queries. This category
contains all functions in the `dns` module but `dns.lookup`. These functions
do not use the same set of configuration files than what `dns.lookup` uses.
For instance, __they do not use the configuration from `/etc/hosts`__. These
functions should be used by developers who do not want to use the underlying
operating system's facilities for name resolution, and instead want to
__always__ perform DNS queries.

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

 >
  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, hostnames) {
        if (err) {
          throw err;
        }
  
        console.log('reverse for ' + a + ': ' + JSON.stringify(hostnames));
      });
    });
  });
<

There are subtle consequences in choosing one or another, please consult the
*node-api-dns_implementation_considerations*
for more information.

==============================================================================
METHODS                                                 *node-api-dns-methods*

------------------------------------------------------------------------------
dns.lookup(hostname[, options], callback)              *node-api-dns.lookup()*

Resolves a hostname (e.g. `'google.com'`) into the first found A (IPv4) or
AAAA (IPv6) record. `options` can be an object or integer. If `options` is
not provided, then IP v4 and v6 addresses are both valid. If `options` is
an integer, then it must be `4` or `6`.

Alternatively, `options` can be an object containing these properties:

* `family` {Number} - The record family. If present, must be the integer
  `4` or `6`. If not provided, both IP v4 and v6 addresses are accepted.
* `hints`: {Number} - If present, it should be one or more of the supported
  `getaddrinfo` flags. If `hints` is not provided, then no flags are passed to
  `getaddrinfo`. Multiple flags can be passed through `hints` by logically
  `OR`ing their values.
  See *node-api-dns_supported_getaddrinfo_flags* below
  for more information on supported flags.
* `all`: {Boolean} - When `true`, the callback returns all resolved addresses
  in an array, otherwise returns a single address. Defaults to `false`.

All properties are optional. An example usage of options is shown below.

 >
  {
    family: 4,
    hints: dns.ADDRCONFIG | dns.V4MAPPED,
    all: false
  }
<

The callback has arguments `(err, address, family)`. `address` is a string
representation of an IP v4 or v6 address. `family` is either the integer 4 or 6
and denotes the family of `address` (not necessarily the value initially passed
to `lookup`).

With the `all` option set, the arguments change to `(err, addresses)`, with
`addresses` being an array of objects with the properties `address` and
`family`.

On error, `err` is an `Error` object, where `err.code` is the error code.
Keep in mind that `err.code` will be set to `'ENOENT'` not only when
the hostname does not exist but also when the lookup fails in other ways
such as no available file descriptors.

`dns.lookup` doesn't necessarily have anything to do with the DNS protocol.
It's only an operating system facility that can associate name with addresses,
and vice versa.

Its implementation can have subtle but important consequences on the behavior
of any io.js program. Please take some time to consult the *node-api-dns_implementation_considerations* before using it.

    
------------------------------------------------------------------------------
dns.lookupService(address, port, callback)      *node-api-dns.lookupService()*

Resolves the given address and port into a hostname and service using
`getnameinfo`.

The callback has arguments `(err, hostname, service)`. The `hostname` and
`service` arguments are strings (e.g. `'localhost'` and `'http'` respectively).

On error, `err` is an `Error` object, where `err.code` is the error code.

    
------------------------------------------------------------------------------
dns.resolve(hostname[, rrtype], callback)             *node-api-dns.resolve()*

Resolves a hostname (e.g. `'google.com'`) into an array of the record types
specified by rrtype.

Valid rrtypes are:

* `'A'` (IPV4 addresses, default)
* `'AAAA'` (IPV6 addresses)
* `'MX'` (mail exchange records)
* `'TXT'` (text records)
* `'SRV'` (SRV records)
* `'PTR'` (used for reverse IP lookups)
* `'NS'` (name server records)
* `'CNAME'` (canonical name records)
* `'SOA'` (start of authority record)

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

On error, `err` is an `Error` object, where `err.code` is
one of the error codes listed below.

    
------------------------------------------------------------------------------
dns.resolve4(hostname, callback)                     *node-api-dns.resolve4()*

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

    
------------------------------------------------------------------------------
dns.resolve6(hostname, callback)                     *node-api-dns.resolve6()*

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

    
------------------------------------------------------------------------------
dns.resolveMx(hostname, callback)                   *node-api-dns.resolveMx()*

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

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

    
------------------------------------------------------------------------------
dns.resolveTxt(hostname, callback)                 *node-api-dns.resolveTxt()*

The same as `dns.resolve()`, but only for text queries (`TXT` records).
`addresses` is a 2-d array of the text records available for `hostname` (e.g.,
`[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]`). Each sub-array contains TXT chunks of
one record. Depending on the use case, the could be either joined together or
treated separately.

    
------------------------------------------------------------------------------
dns.resolveSrv(hostname, callback)                 *node-api-dns.resolveSrv()*

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

    
------------------------------------------------------------------------------
dns.resolveSoa(hostname, callback)                 *node-api-dns.resolveSoa()*

The same as `dns.resolve()`, but only for start of authority record queries
(`SOA` record).

`addresses` is an object with the following structure:

 >
  {
    nsname: 'ns.example.com',
    hostmaster: 'root.example.com',
    serial: 2013101809,
    refresh: 10000,
    retry: 2400,
    expire: 604800,
    minttl: 3600
  }
<

    
------------------------------------------------------------------------------
dns.resolveNs(hostname, callback)                   *node-api-dns.resolveNs()*

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

    
------------------------------------------------------------------------------
dns.resolveCname(hostname, callback)             *node-api-dns.resolveCname()*

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

    
------------------------------------------------------------------------------
dns.reverse(ip, callback)                             *node-api-dns.reverse()*

Reverse resolves an ip address to an array of hostnames.

The callback has arguments `(err, hostnames)`.

On error, `err` is an `Error` object, where `err.code` is
one of the error codes listed below.

    
------------------------------------------------------------------------------
dns.getServers()                                   *node-api-dns.getServers()*

Returns an array of IP addresses as strings that are currently being used for
resolution

    
------------------------------------------------------------------------------
dns.setServers(servers)                            *node-api-dns.setServers()*

Given an array of IP addresses as strings, set them as the servers to use for
resolving

If you specify a port with the address it will be stripped, as the underlying
library doesn't support that.

This will throw if you pass invalid input.

    

==============================================================================
PROPERTIES                                           *node-api-dns-properties*

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