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

snippet

const dns = require('dns');
dns.lookup('www.rookienerd.com', (err, addresses, family) => {
  console.log('addresses:', addresses);
  console.log('family:',family);
});

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

snippet

node dns_example1.js

Node.js DNS Example 2

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

File: dns_example2.js

snippet

const dns = require('dns');
dns.resolve4('www.rookienerd.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:

snippet

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

snippet

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:

snippet

node dns_example3.js