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Node.js – dnsPromises.lookupService() Method
The dns.lookupService() method resolves the 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. The difference between the dnsPromises and dns module is that dnsPromises provides an alternative way to asynchronous DNS methods that return Promise objects instead of callbacks.
Syntax
dnsPromises.lookupService(address, port)
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.
Example 1
Create a file with the name "lookupService.js" and copy the following code snippet. After creating the file, use the command "node lookupService.js" to run this code.
// dns.lookupService() Demo Example // Importing the dns module const dns = require('dns'); const dnsPromises = dns.promises; // Passing the IP address and port dnsPromises.lookupService('127.0.0.1', 22).then((response) => { console.log(response.hostname, response.service); });
Output
localhost ssh
Example 2
// dns.lookupService() Demo Example // Importing the dns module const dns = require('dns'); const dnsPromises = dns.promises; // Passing the below options to lookup const options = { //IPv4 family: 4, hints: dns.ADDRCONFIG | dns.V4MAPPED, }; dnsPromises.lookup('tutorialspoint.com', options).then((response) => { if(response){ console.log(response); // Passing dns value to lookupservice dnsPromises.lookupService(response.address, 80).then((res) => { console.log(res.hostname, res.service); }); } });
Output
C:\home
ode>> node lookupService.js { address: '95.217.74.146', family: 4 } static.146.74.217.95.clients.your-server.de http