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

const dns = require('dns');  

dns.lookup('www.javatpoint.com', (err, addresses, family) => {  

  console.log('addresses:', addresses);  

  console.log('family:',family);  

});  

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

node dns_example1.js  

Node.js DNS Example 2

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

File: dns_example2.js

const dns = require('dns');  

dns.resolve4('www.javatpoint.com', (err, addresses) => {  

  if (err) throw err;  

  console.log(`addresses: ${JSON.stringify(addresses)}`);  

  addresses.forEach((a) => {  

    dns.reverse(a, (err, hostnames) => {  

      if (err) {  

        throw err;  

      }  

      console.log(`reverse for ${a}: ${JSON.stringify(hostnames)}`);  

    });  

  });  

});  

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

node dns_example2.js  

Node.js DNS Example 3

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

File: dns_example3.js

const dns = require('dns');  

dns.lookupService('127.0.0.1', 22, (err, hostname, service) => {  

  console.log(hostname, service);  

    // Prints: localhost  

}); 

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

node dns_example3.js