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Node.js DNS


The Node.js DNS module contains methods to get data of given hostname. We should see the list of commonly utilized DNS capacities:
  • 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.welookups.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 case of resolve4() and switch() functions.

File: dns_example2.js

  1. const dns = require('dns');  
  2. dns.resolve4('www.welookups.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 order brief and run the accompanying 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

    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. });  





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