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Node.js DNS


The Node.js DNS module contains methods to get information of given hostname. Let’s see the list of commonly used DNS functions:

  • dns.getServers()
  • dns.setServers(servers)
  • dns.lookup(hostname[, options], callback)
  • dns.lookupService(address, port, callback)
  • dns.resolve(hostname[, rrtype], callback)
  • dns.resolve4(hostname, callback)
  • dns.resolve6(hostname, callback)
  • dns.resolveCname(hostname, callback)
  • dns.resolveMx(hostname, callback)
  • dns.resolveNs(hostname, callback)
  • dns.resolveSoa(hostname, callback)
  • dns.resolveSrv(hostname, callback)
  • dns.resolvePtr(hostname, callback)
  • dns.resolveTxt(hostname, callback)
  • dns.reverse(ip, callback)

Node.js DNS Example 1

Let’s see the example of dns.lookup() function.

File: dns_example1.js

  1. const dns = require(‘dns’);
  2. dns.lookup(‘www.Kreationnext.com’, (err, addresses, family) => {
  3.   console.log(‘addresses:’, addresses);
  4.   console.log(‘family:’,family);
  5. });

Open Node.js command prompt and run the following code:

  1. node dns_example1.js

dns_example1

Node.js DNS Example 2

Let’s see the example of resolve4() and reverse() functions.

File: dns_example2.js

  1. const dns = require(‘dns’);
  2. dns.resolve4(‘www.Kreationnext.com’, (err, addresses) => {
  3.   if (err) throw err;
  4.   console.log(`addresses: ${JSON.stringify(addresses)}`);
  5.   addresses.forEach((a) => {
  6.     dns.reverse(a, (err, hostnames) => {
  7.       if (err) {
  8.         throw err;
  9.       }
  10.       console.log(`reverse for ${a}: ${JSON.stringify(hostnames)}`);
  11.     });
  12.   });
  13. });

Open Node.js command prompt and run the following code:

  1. node dns_example2.js

dns_example2.jpg

Node.js DNS Example 3

Let’s take an example to print the localhost name using lookupService() function.

File: dns_example3.js

  1. const dns = require(‘dns’);
  2. dns.lookupService(‘127.0.0.1’, 22, (err, hostname, service) => {
  3.   console.log(hostname, service);
  4.     // Prints: localhost
  5. });

Open Node.js command prompt and run the following code:

  1. node dns_example3.js

dns_example3.jpg

 

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