Node.js dnsPromises.lookupService() Method
Last Updated :
13 Oct, 2021
The dnsPromises.lookupService() method is an inbuilt application programming interface of the promises object of dns module which is used to resolve the addresses and port number to hostname and service using operating system’s underlying getnameinfo implementation.
Syntax:
dnsPromises.lookupService( address, port )
Parameters: This method has two parameters as mentioned above and described below:
- address: It specifies a string which denotes address to be resolved.
- port: It is a number that specifies the port number of the address whose service to be resolved.
Return Value: This method returns error, hostname and services.
Below examples illustrate the use of dnsPromises.lookupService() method in Node.js:
Example 1:
const dns = require( 'dns' );
const dnsPromises = dns.promises;
dnsPromises.lookupService( '127.0.0.1' , 22).then((res) => {
console.log(res.hostname, res.service);
});
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Output: Here name of my computer is my-lappy
my-lappy ssh
Example 2:
const dns = require( 'dns' );
const dnsPromises = dns.promises;;
const options = {
family: 4,
hints: dns.ADDRCONFIG | dns.V4MAPPED,
};
dnsPromises.lookup( 'geeksforgeeks.org' , options).then((response) => {
if (response){
console.log(response);
dnsPromises.lookupService(response.address, 80).then((res) => {
console.log(res.hostname, res.service);
});
}
});
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Output:
{ address: '34.218.62.116', family: 4 }
ec2-34-218-62-116.us-west-2.compute.amazonaws.com 334
Note: The above program will compile and run by using the node index.js
command.
Reference: https://nodejs.org/api/dns.html#dns_dnspromises_lookupservice_address_port
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