What is 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.javatpoint.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  

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.javatpoint.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  

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