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Node.js – dns.lookupService() Method
The dns.lookupService() method resolves a given address and port into a hostname and service. This method uses the operating system's underlying getnameinfo implementation. A TypeError will be thrown if the address is not a valid IP address.
Syntax
dns.lookupService(address, port, callback)
Parameters
address - This parameter takes input for the IP address that needs to be resolved.
port - This parameter takes input for the port number that is attached with the IP address.
callback - It will catch errors, if any.
Example 1
Create a file with the name "lookupService.js" and copy the following code. After creating the file, use the command "node lookupService.js" to run this code as shown in the example below −
// dns.lookupService() Demo Example // Importing the dns module const dns = require('dns'); // Passing the IP address and port dns.lookupService('127.0.0.1', 22, (err, hostname, service) => { console.log(hostname, service); });
Output
It will produce the following output −
localhost ssh
Example 2
Let's take another example −
// dns.lookupService() Demo Example // Importing the dns module const dns = require('dns'); // Passing the below options to lookup const options = { //IPv4 family: 4, hints: dns.ADDRCONFIG | dns.V4MAPPED, }; dns.lookup('tutorialsPoint.com', options, (err, address, family) => { console.log('address:', address); if(err){ console.log(err.stack); } else{ // Calling dns.lookupService() method // to retrieve details of IP address dns.lookupService(address, 80,(err, hostname, service) => { if(err){ console.log(err.stack); } // Printing hostname and service // as callback console.log(hostname, service); }); } });
Output
address: 157.90.94.102 tutorialspoint.com http
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