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Guide to using the DNS Module in Node JS
Guide to using the DNS Module in Node JS

Tech Updates

Guide to using the DNS Module in Node JS

Introducing DNS in Node.JS

Node.JS DNS is a module that is used for DNS lookups as well as underlying operating system name resolution. For lookups, the Domain Name System (DNS) does not always employ the DNS protocol. The key advantage of DNS is that the user does not have to memorize all of the IP addresses because DNS provides a good method for converting domain or subdomain names to IP addresses. This Node.JS DNS contains several methods for retrieving hostname information. You can always acquire the Node JS certification from a popular and certified institution such as KnowledgeHut..

What is DNS and why is it important?

DNS is an abbreviation for Domain Name System. The DNS’s principal function is to convert the IP Handle, which is a numerical label provided to your computer. IP addresses are regarded as computer system names on a network and are used to distinguish between various units and their territories.

As a result, DNS can be thought of as the Internet’s phonebook. When we enter a URL into our browser, such as, it is routed to the Name Server, which changes it to an IP address (like This is then transmitted to the appropriate server for further processing.

The DNS Module

We use this module to perform a real DNS look-up & to utilize the already present Operating System’s name resolution capabilities. This module offers an “Asynchronous Network Wrapper (ANW)” & you can import it with the syntax shown below. var dnsServer = require(‘dns’); the syntax is used to import this module, which offers an asynchronous network wrapper.

Steps to use the DNS Module in Node JS

Step 1: Make one new file/folder called VSCodeDNSServer. Open the “Visual Studio”, then navigate to this file/folder using the Tools > Open Folder menu. Make a new file or directory called Scripts in the VSCodeDNSServer file.

Step 2: To download the Node.js debugging tools for the app, launch the Node.js run command and browse the VSCodeDNSServer file, then you have to run the given below commands.

install npm -g tsd

The TypeScript Description for the app will be imported as a result of this.

To activate Node.js debugging tools for the new work, execute the following line from your Command Prompt.

—action install tsd query node

Step 3: Create one new file called app.js in the Scripts folder and paste the below program into it.


var dns = require(‘dns’);


var params =



var serverName =




discoverAddressLookupReverse(operationType, tcpip) {

    dns.reverse(tcpip, function (err, domainNames) {

        if (err) {


        } else

            if (domainNames.length > 1) {

               console.log(operationType + ‘ domain names for the address ‘ +

tcpip + ‘ for server ‘ + serverName)

            } else {

             console.log(operationType + ‘ domain name for the address’ +

tcpip + ‘ for server ‘ + serverName);






function (err, addr) {

    if (err) {

        console.log(‘Something is Wrong ‘ + err.message);



    discoverAddressLookupReverse(‘resolve’, addr.toString());




function (err, addr, family) {

    if (err) {

        console.log(‘Something is Wrong ‘ + err.message);



    discoverAddressLookupReverse(‘lookup’, addr.toString());


The following are the specs for the aforementioned code:

  • Download and install the DNS Module that we can use to bring up and resolve domain names.
  • Double-check the domain you typed into the command line. For the Node program, the domain, for example,, is on the following command index
  • Returns the domain server’s hostname.
  • Its characteristics The type of operation, such as Resolving or Search, is the first of two inputs to discoverAddressLookupReverse (). The second input represents the domain’s address details. This method employs the DNS module’s reserve () function to reverse resolve an Ip to a list of hostnames. Finally, discoverAddressLookupReverse () displays the resolution and lookup for the hostname.
  • A domain must be chosen.
  • Locate the first IPv4 or IPv6 address that corresponds to the hostname.

Step 4:Choose settings by right-clicking the app.js file. Click the Command Line, which will start the concerned command prompt where you can work with the given command.

Error Code: When we employ any of the DNS or its promise strategies, a slew of issues might occur. The mistakes that we can make are listed below.

  • NODATA: The DNS server delivered an empty response.
  • FORMERR: DNS server believes the inquiry was incorrectly formed.
  • SERVFAIL: The DNS server returned a typical error.
  • NOTFOUND: No area identifier was found.
  • NOTIMP: The DNS server did not perform the requested action.
  • REFUSED: The DNS server rejected the query.
  • BADQUERY: An incorrectly formed DNS inquiry.
  • BADNAME: Incorrectly formatted host identifier.
  • BADFAMILY: Unsupported home management.
  • BADRESP: Incorrectly formatted DNS response.
  • CONNREFUSED: Unable to connect to DNS servers.
  • TIMEOUT: A timeout occurred when attempting to reach DNS servers.
  • EOF: End of file.
  • FILE: Error when examining the file.
  • NOMEM: derived from recollection.
  • DESTRUCTION: The channel is being demolished.
  • BADSTR: Incorrectly formatted string.
  • Unlawful flags are described by BADFLAGS.
  • NONAME: The given host identifier should not be a number.
  • BADHINTS: Illegal hints flags are specified.
  • NOTINITIALIZED: c-ares library initialization was not completed.
  • LOADIPHLPAPI: Failed to load iphlpapi.dll.
  • ADDRGETNETWORKPARAMS: Couldn’t find the GetNetworkParams function.
  • CANCELLED: DNS query has been canceled.

Concerns with Implementation

There is a distinction between previous dns.lookup() runs and other DNS techniques such as dns.resolve() and dns.reverse() runs. The “dns.lookup()” function will always resolve a provided identify in the same way as the ping command does. It does not generate a community name and is executed as a synchronous name to getaddrinfo().

Otherwise, the functions dns.resolve() and dns.reverse() are carried out honestly, and hence they do not need the getaddrinfo() operation. They will always do a DNS query on the community. As a result, the outcome is extra accurate and up to date.


As a result, the above variances can have significant consequences for our NodeJS software and must be considered thoroughly. Hope! You find the above information useful and utilize it efficiently for using the DNS Module in NodeJS. If you are looking for the node js certification the KnowledgHut Node JS training would be a great choice to opt for and kick start your career.

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