Node.js dns.lookupService() Method

// Accessing dns module
const dns = require('dns');

// Calling dns.lookupService() method for
// 127.0.0.1 port  number 22
dns.lookupService('127.0.0.1', 22,
         (err, hostname, service) => {
        
    // Printing hostname and service as callback
    console.log(hostname, service);
});

// Accessing dns module
const dns = require('dns');
 
// Setting options for dns.lookup() method
const options = {
     
    // Setting family as 4 i.e. IPv4
    family: 4,
    hints: dns.ADDRCONFIG | dns.V4MAPPED,
};
 
dns.lookup('www.geeksforgeeks.org', 
        options, (err, address, family) => {
     
    console.log('address:', address);
        if(err){
            console.log(err.stack);
        } else{
 
        // Calling dns.lookupService() method 
        dns.lookupService(address, 80,
                 (err, hostname, service) => {
            if(err){
                console.log(err.stack);
            }
             
            // Printing hostname and service
            // as callback
            console.log(hostname, service);
        });
    }
});