Node

dns/promises

dns/promises

The dns.promises API provides an alternative set of asynchronous DNS methods that return Promise objects rather than using callbacks. The API is accessible via import { promises as dnsPromises } from 'node:dns' or import dnsPromises from 'node:dns/promises'.

Usage in Deno

import * as mod from "node:dns/promises";

Classes

Resolver

An independent resolver for DNS requests.

Functions

getDefaultResultOrder

Get the default value for verbatim in lookup and dnsPromises.lookup(). The value could be:

getServers

Returns an array of IP address strings, formatted according to RFC 5952, that are currently configured for DNS resolution. A string will include a port section if a custom port is used.

lookup

Resolves a host name (e.g. 'nodejs.org') into the first found A (IPv4) or AAAA (IPv6) record. All option properties are optional. If options is an integer, then it must be 4 or 6 – if options is not provided, then IPv4 and IPv6 addresses are both returned if found.

lookupService

Resolves the given address and port into a host name and service using the operating system's underlying getnameinfo implementation.

resolve

Uses the DNS protocol to resolve a host name (e.g. 'nodejs.org') into an array of the resource records. When successful, the Promise is resolved with an array of resource records. The type and structure of individual results vary based on rrtype:

resolve4

Uses the DNS protocol to resolve IPv4 addresses (A records) for the hostname. On success, the Promise is resolved with an array of IPv4 addresses (e.g. ['74.125.79.104', '74.125.79.105', '74.125.79.106']).

resolve6

Uses the DNS protocol to resolve IPv6 addresses (AAAA records) for the hostname. On success, the Promise is resolved with an array of IPv6 addresses.

resolveAny

Uses the DNS protocol to resolve all records (also known as ANY or * query). On success, the Promise is resolved with an array containing various types of records. Each object has a property type that indicates the type of the current record. And depending on the type, additional properties will be present on the object:

resolveCaa

Uses the DNS protocol to resolve CAA records for the hostname. On success, the Promise is resolved with an array of objects containing available certification authority authorization records available for the hostname (e.g. [{critical: 0, iodef: 'mailto:pki@example.com'},{critical: 128, issue: 'pki.example.com'}]).

resolveCname

Uses the DNS protocol to resolve CNAME records for the hostname. On success, the Promise is resolved with an array of canonical name records available for the hostname (e.g. ['bar.example.com']).

resolveMx

Uses the DNS protocol to resolve mail exchange records (MX records) for the hostname. On success, the Promise is resolved with an array of objects containing both a priority and exchange property (e.g.[{priority: 10, exchange: 'mx.example.com'}, ...]).

resolveNaptr

Uses the DNS protocol to resolve regular expression-based records (NAPTR records) for the hostname. On success, the Promise is resolved with an array of objects with the following properties:

resolveNs

Uses the DNS protocol to resolve name server records (NS records) for the hostname. On success, the Promise is resolved with an array of name server records available for hostname (e.g.['ns1.example.com', 'ns2.example.com']).

resolvePtr

Uses the DNS protocol to resolve pointer records (PTR records) for the hostname. On success, the Promise is resolved with an array of strings containing the reply records.

resolveSoa

Uses the DNS protocol to resolve a start of authority record (SOA record) for the hostname. On success, the Promise is resolved with an object with the following properties:

resolveSrv

Uses the DNS protocol to resolve service records (SRV records) for the hostname. On success, the Promise is resolved with an array of objects with the following properties:

resolveTxt

Uses the DNS protocol to resolve text queries (TXT records) for the hostname. On success, the Promise is resolved with a two-dimensional 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, these could be either joined together or treated separately.

reverse

Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an array of host names.

setDefaultResultOrder

Set the default value of order in dns.lookup() and [lookup](/api/node/dns/promises/. The value could be:

setServers

Sets the IP address and port of servers to be used when performing DNS resolution. The servers argument is an array of RFC 5952 formatted addresses. If the port is the IANA default DNS port (53) it can be omitted.

Variables

ADDRGETNETWORKPARAMS

No documentation available

BADFAMILY

No documentation available

BADFLAGS

No documentation available

BADHINTS

No documentation available

BADNAME

No documentation available

BADQUERY

No documentation available

BADRESP

No documentation available

BADSTR

No documentation available

CANCELLED

No documentation available

CONNREFUSED

No documentation available

DESTRUCTION

No documentation available

EOF

No documentation available

FILE

No documentation available

FORMERR

No documentation available

LOADIPHLPAPI

No documentation available

NODATA

No documentation available

NOMEM

No documentation available

NONAME

No documentation available

NOTFOUND

No documentation available

NOTIMP

No documentation available

NOTINITIALIZED

No documentation available

REFUSED

No documentation available

SERVFAIL

No documentation available

TIMEOUT

No documentation available

class Resolver

Usage in Deno

import { Resolver } from "node:dns/promises";

An independent resolver for DNS requests.

Creating a new resolver uses the default server settings. Setting the servers used for a resolver using resolver.setServers() does not affect other resolvers:

import { promises } from 'node:dns';
const resolver = new promises.Resolver();
resolver.setServers(['4.4.4.4']);

// This request will use the server at 4.4.4.4, independent of global settings.
resolver.resolve4('example.org').then((addresses) => {
  // ...
});

// Alternatively, the same code can be written using async-await style.
(async function() {
  const addresses = await resolver.resolve4('example.org');
})();

The following methods from the dnsPromises API are available:

resolver.getServers()
resolver.resolve()
resolver.resolve4()
resolver.resolve6()
resolver.resolveAny()
resolver.resolveCaa()
resolver.resolveCname()
resolver.resolveMx()
resolver.resolveNaptr()
resolver.resolveNs()
resolver.resolvePtr()
resolver.resolveSoa()
resolver.resolveSrv()
resolver.resolveTxt()
resolver.reverse()
resolver.setServers()

Constructors #

#Resolver(options?: ResolverOptions)

new

Properties #

Methods #

#cancel(): void

Cancel all outstanding DNS queries made by this resolver. The corresponding callbacks will be called with an error with code ECANCELLED.

#setLocalAddress(ipv4?: string,
ipv6?: string,
): void

The resolver instance will send its requests from the specified IP address. This allows programs to specify outbound interfaces when used on multi-homed systems.

If a v4 or v6 address is not specified, it is set to the default and the operating system will choose a local address automatically.

The resolver will use the v4 local address when making requests to IPv4 DNS servers, and the v6 local address when making requests to IPv6 DNS servers. The rrtype of resolution requests has no impact on the local address used.

function getDefaultResultOrder

Usage in Deno

import { getDefaultResultOrder } from "node:dns/promises";

#getDefaultResultOrder(): "ipv4first" | "verbatim"

Get the default value for verbatim in lookup and dnsPromises.lookup(). The value could be:

ipv4first: for verbatim defaulting to false.
verbatim: for verbatim defaulting to true.

Return Type #

"ipv4first" | "verbatim"

function getServers

Usage in Deno

import { getServers } from "node:dns/promises";

#getServers(): string[]

Returns an array of IP address strings, formatted according to RFC 5952, that are currently configured for DNS resolution. A string will include a port section if a custom port is used.

[
  '4.4.4.4',
  '2001:4860:4860::8888',
  '4.4.4.4:1053',
  '[2001:4860:4860::8888]:1053',
]

Return Type #

string[]

function lookup

Usage in Deno

import { lookup } from "node:dns/promises";

Overload 1

#lookup(hostname: string,
family: number,
): Promise<LookupAddress>

With the all option set to true, the Promise is resolved with addresses being an array of objects with the properties address and family.

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

dnsPromises.lookup() does not necessarily have anything to do with the DNS protocol. The implementation uses an operating system facility that can associate names with addresses and vice versa. This implementation can have subtle but important consequences on the behavior of any Node.js program. Please take some time to consult the Implementation considerations section before using dnsPromises.lookup().

Example usage:

import dns from 'node:dns';
const dnsPromises = dns.promises;
const options = {
  family: 6,
  hints: dns.ADDRCONFIG | dns.V4MAPPED,
};

dnsPromises.lookup('example.com', options).then((result) => {
  console.log('address: %j family: IPv%s', result.address, result.family);
  // address: "2606:2800:220:1:248:1893:25c8:1946" family: IPv6
});

// When options.all is true, the result will be an Array.
options.all = true;
dnsPromises.lookup('example.com', options).then((result) => {
  console.log('addresses: %j', result);
  // addresses: [{"address":"2606:2800:220:1:248:1893:25c8:1946","family":6}]
});

Parameters #

#hostname: string

#family: number

Return Type #

Promise<LookupAddress>

Overload 2

#lookup(hostname: string,
options: LookupOneOptions,
): Promise<LookupAddress>

Parameters #

#hostname: string

#options: LookupOneOptions

Return Type #

Promise<LookupAddress>

Overload 3

#lookup(hostname: string,
options: LookupAllOptions,
): Promise<LookupAddress[]>

Parameters #

#hostname: string

#options: LookupAllOptions

Return Type #

Promise<LookupAddress[]>

Overload 4

#lookup(hostname: string,
options: LookupOptions,
): Promise<LookupAddress | LookupAddress[]>

Parameters #

#hostname: string

#options: LookupOptions

Return Type #

Promise<LookupAddress | LookupAddress[]>

Overload 5

#lookup(hostname: string): Promise<LookupAddress>

Parameters #

#hostname: string

Return Type #

Promise<LookupAddress>

function lookupService

Usage in Deno

import { lookupService } from "node:dns/promises";

#lookupService(address: string,
port: number,
): Promise<{ hostname: string; service: string;  }>

Resolves the given address and port into a host name and service using the operating system's underlying getnameinfo implementation.

If address is not a valid IP address, a TypeError will be thrown. The port will be coerced to a number. If it is not a legal port, a TypeError will be thrown.

On error, the Promise is rejected with an Error object, where err.code is the error code.

import dnsPromises from 'node:dns';
dnsPromises.lookupService('127.0.0.1', 22).then((result) => {
  console.log(result.hostname, result.service);
  // Prints: localhost ssh
});

Parameters #

#address: string

#port: number

Return Type #

Promise<{ hostname: string; service: string; }>

function resolve

Usage in Deno

import { resolve } from "node:dns/promises";

Overload 1

#resolve(hostname: string): Promise<string[]>

#resolve(hostname: string,
rrtype: string,
): Promise<string[]
 | MxRecord[]
 | NaptrRecord[]
 | SoaRecord
 | SrvRecord[]
 | string[][]
 | AnyRecord[]
>

Parameters #

#hostname: string

#rrtype: string

Return Type #

Promise<string[]
 | MxRecord[]
 | NaptrRecord[]
 | SoaRecord
 | SrvRecord[]
 | string[][]
 | AnyRecord[]
>

function resolve4

Usage in Deno

import { resolve4 } from "node:dns/promises";

function resolve6

Usage in Deno

import { resolve6 } from "node:dns/promises";

Overload 1

#resolve6(hostname: string): Promise<string[]>

Usage in Deno

import { resolveAny } from "node:dns/promises";

#resolveAny(hostname: string): Promise<AnyRecord[]>

Here is an example of the result object:

[ { type: 'A', address: '127.0.0.1', ttl: 299 },
  { type: 'CNAME', value: 'example.com' },
  { type: 'MX', exchange: 'alt4.aspmx.l.example.com', priority: 50 },
  { type: 'NS', value: 'ns1.example.com' },
  { type: 'TXT', entries: [ 'v=spf1 include:_spf.example.com ~all' ] },
  { type: 'SOA',
    nsname: 'ns1.example.com',
    hostmaster: 'admin.example.com',
    serial: 156696742,
    refresh: 900,
    retry: 900,
    expire: 1800,
    minttl: 60 } ]

Parameters #

#hostname: string

Return Type #

Promise<AnyRecord[]>

function resolveCaa

Usage in Deno

import { resolveCaa } from "node:dns/promises";

#resolveCaa(hostname: string): Promise<CaaRecord[]>

Parameters #

#hostname: string

Return Type #

Promise<CaaRecord[]>

function resolveCname

Usage in Deno

import { resolveCname } from "node:dns/promises";

#resolveCname(hostname: string): Promise<string[]>

Parameters #

#hostname: string

Return Type #

Promise<string[]>

function resolveMx

Usage in Deno

import { resolveMx } from "node:dns/promises";

#resolveMx(hostname: string): Promise<MxRecord[]>

Parameters #

#hostname: string

Return Type #

Promise<MxRecord[]>

function resolveNaptr

Usage in Deno

import { resolveNaptr } from "node:dns/promises";

#resolveNaptr(hostname: string): Promise<NaptrRecord[]>

Uses the DNS protocol to resolve regular expression-based records (NAPTR records) for the hostname. On success, the Promise is resolved with an array of objects with the following properties:

flags
service
regexp
replacement
order
preference

{
  flags: 's',
  service: 'SIP+D2U',
  regexp: '',
  replacement: '_sip._udp.example.com',
  order: 30,
  preference: 100
}

Parameters #

#hostname: string

Return Type #

Promise<NaptrRecord[]>

function resolveNs

Usage in Deno

import { resolveNs } from "node:dns/promises";

#resolveNs(hostname: string): Promise<string[]>

Parameters #

#hostname: string

Return Type #

Promise<string[]>

function resolvePtr

Usage in Deno

import { resolvePtr } from "node:dns/promises";

#resolvePtr(hostname: string): Promise<string[]>

Uses the DNS protocol to resolve pointer records (PTR records) for the hostname. On success, the Promise is resolved with an array of strings containing the reply records.

Parameters #

#hostname: string

Return Type #

Promise<string[]>

function resolveSoa

Usage in Deno

import { resolveSoa } from "node:dns/promises";

#resolveSoa(hostname: string): Promise<SoaRecord>

Uses the DNS protocol to resolve a start of authority record (SOA record) for the hostname. On success, the Promise is resolved with an object with the following properties:

nsname
hostmaster
serial
refresh
retry
expire
minttl

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

Parameters #

#hostname: string

Return Type #

Promise<SoaRecord>

function resolveSrv

Usage in Deno

import { resolveSrv } from "node:dns/promises";

#resolveSrv(hostname: string): Promise<SrvRecord[]>

Uses the DNS protocol to resolve service records (SRV records) for the hostname. On success, the Promise is resolved with an array of objects with the following properties:

priority
weight
port
name

{
  priority: 10,
  weight: 5,
  port: 21223,
  name: 'service.example.com'
}

Parameters #

#hostname: string

Return Type #

Promise<SrvRecord[]>

function resolveTxt

Usage in Deno

import { resolveTxt } from "node:dns/promises";

#resolveTxt(hostname: string): Promise<string[][]>

Parameters #

#hostname: string

Return Type #

Promise<string[][]>

function reverse

Usage in Deno

import { reverse } from "node:dns/promises";

#reverse(ip: string): Promise<string[]>

Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an array of host names.

On error, the Promise is rejected with an Error object, where err.code is one of the DNS error codes.

Parameters #

#ip: string

Return Type #

Promise<string[]>

function setDefaultResultOrder

Usage in Deno

import { setDefaultResultOrder } from "node:dns/promises";

#setDefaultResultOrder(order: "ipv4first"
 | "ipv6first"
 | "verbatim"): void

Set the default value of order in dns.lookup() and [lookup](/api/node/dns/promises/. The value could be:

ipv4first: sets default order to ipv4first.
ipv6first: sets default order to ipv6first.
verbatim: sets default order to verbatim.

The default is verbatim and dnsPromises.setDefaultResultOrder() have higher priority than --dns-result-order. When using worker threads, dnsPromises.setDefaultResultOrder() from the main thread won't affect the default dns orders in workers.

Parameters #

#order: "ipv4first"
 | "ipv6first"
 | "verbatim"

must be 'ipv4first', 'ipv6first' or 'verbatim'.

Return Type #

void

function setServers

Usage in Deno

import { setServers } from "node:dns/promises";

#setServers(servers: readonly string[]): void

dnsPromises.setServers([
  '4.4.4.4',
  '[2001:4860:4860::8888]',
  '4.4.4.4:1053',
  '[2001:4860:4860::8888]:1053',
]);

An error will be thrown if an invalid address is provided.

The dnsPromises.setServers() method must not be called while a DNS query is in progress.

This method works much like resolve.conf. That is, if attempting to resolve with the first server provided results in a NOTFOUND error, the resolve() method will not attempt to resolve with subsequent servers provided. Fallback DNS servers will only be used if the earlier ones time out or result in some other error.

Parameters #

#servers: readonly string[]

import { TIMEOUT } from "node:dns/promises";

Type #

"ETIMEOUT"