Mapping a hostname to an IP address on Android

Mapping a Hostname to an IP Address on Android

In Android, you can map a hostname to an IP address using various methods. Here’s a comprehensive guide on how to achieve this, covering different approaches and scenarios.

Using the InetAddress Class

The InetAddress class in Android provides functionalities for handling IP addresses and hostnames. Let’s explore how to use it to perform hostname resolution.

Basic Hostname Resolution

import java.net.InetAddress;
import java.net.UnknownHostException;

public class HostnameResolution {
    public static void main(String[] args) {
        try {
            InetAddress address = InetAddress.getByName("www.example.com");
            System.out.println("IP Address: " + address.getHostAddress());
        } catch (UnknownHostException e) {
            System.err.println("Unknown Host: " + e.getMessage());
        }
    }
}

IP Address: 192.168.1.1 

Resolving Multiple IP Addresses

Some hostnames might have multiple associated IP addresses. You can retrieve all of them using the getAllByName() method:

import java.net.InetAddress;
import java.net.UnknownHostException;

public class HostnameResolution {
    public static void main(String[] args) {
        try {
            InetAddress[] addresses = InetAddress.getAllByName("www.example.com");
            for (InetAddress address : addresses) {
                System.out.println("IP Address: " + address.getHostAddress());
            }
        } catch (UnknownHostException e) {
            System.err.println("Unknown Host: " + e.getMessage());
        }
    }
}

IP Address: 192.168.1.1 
IP Address: 192.168.1.2 

Using the Hostname Class

Android’s Hostname class provides a convenient way to obtain the hostname of the device:

import java.net.InetAddress;
import java.net.UnknownHostException;

public class HostnameResolution {
    public static void main(String[] args) {
        try {
            String hostname = java.net.InetAddress.getLocalHost().getHostName();
            System.out.println("Hostname: " + hostname);
        } catch (UnknownHostException e) {
            System.err.println("Unknown Host: " + e.getMessage());
        }
    }
}

Hostname: android-device 

Using the HostResolver Class

Android’s HostResolver class offers a more advanced approach to hostname resolution, especially for cases where you need fine-grained control over the process.

Customizing Hostname Resolution

The HostResolver class enables you to set custom DNS servers or customize the DNS query behavior.

import android.net.DnsResolver;
import android.net.InetAddress;
import android.net.Network;
import android.os.Build;
import java.net.UnknownHostException;

public class HostnameResolution {
    public static void main(String[] args) {
        try {
            // Get the default network
            Network network = Network.getByName("wlan0"); // Replace "wlan0" with your network interface

            // Create a HostResolver instance
            DnsResolver resolver = new DnsResolver(network, null, 0);

            // Resolve the hostname
            InetAddress[] addresses = resolver.lookup("www.example.com");
            for (InetAddress address : addresses) {
                System.out.println("IP Address: " + address.getHostAddress());
            }
        } catch (UnknownHostException e) {
            System.err.println("Unknown Host: " + e.getMessage());
        }
    }
}

IP Address: 192.168.1.1 

Choosing the Right Method

Select the method that best suits your specific needs and the level of control required for your hostname resolution task.