Node.js DNS

Node.js DNS module provides a way to do name resolution between domain names and IP addresses. It is mainly used in network programming and for developing web applications.

Methods

The DNS module offers various methods to perform name resolution:

dns.lookup()

This method resolves a hostname or IP address. It takes two arguments: the hostname and an optional options object. The method returns an IP address.

const dns = require('dns');

dns.lookup('www.google.com', (err, address, family) => {
  console.log(`IP Address: ${address}`);
});

dns.reverse()

This method does the opposite of the dns.lookup() method. It takes an IP address as its argument and returns a hostname.

dns.reverse('8.8.8.8', (err, hostnames) => {
  console.log(`Hostname: ${hostnames}`);
});

Constants

The DNS module also provides some constants that can be useful in network programming:

dns.ADDRCONFIG

This constant specifies that the dns.lookup() method should only resolve IP addresses that are configured on the host itself.

dns.V4MAPPED

This constant specifies that the dns.lookup() method should return IPv6 addresses as well, but only if no IPv4 addresses are found.

Error Handling

The DNS module can throw errors in various situations, such as when a hostname cannot be resolved. To handle these errors, you can use try-catch blocks or the standard Node.js error handling mechanism.

try {
  const address = dns.lookupSync('badhost.badtld');
  console.log(`IP Address: ${address}`);
} catch (err) {
  console.error(err);
}

Conclusion

The Node.js DNS module provides a simple and reliable way to perform name resolution in your Node.js applications. By using the methods provided by the module, you can easily lookup hostnames and IP addresses, and handle errors in a graceful manner.