Thread: How to Find machines connected to a network

This code will effectively ping an IP range looking for machines on a network.

It isn't the fastest method but works none the less.

import java.io.IOException;
import java.net.InetAddress;
 
public class NetworkPing {
 
    /**
     * JavaProgrammingForums.com
     */
    public static void main(String[] args) throws IOException {
 
        InetAddress localhost = InetAddress.getLocalHost();
        // this code assumes IPv4 is used
        byte[] ip = localhost.getAddress();
 
        for (int i = 1; i <= 254; i++)
        {
            ip[3] = (byte)i;
            InetAddress address = InetAddress.getByAddress(ip);
        if (address.isReachable(1000))
        {
            System.out.println(address + " machine is turned on and can be pinged");
        }
        else if (!address.getHostAddress().equals(address.getHostName()))
        {
            System.out.println(address + " machine is known in a DNS lookup");
        }
        else
        {
            System.out.println(address + " the host address and host name are equal, meaning the host name could not be resolved");
        }
        }
 
    }
}

great program sir;
but will you please explain this part of code

InetAddress localhost = InetAddress.getLocalHost();
// this code assumes IPv4 is used
byte[] ip = localhost.getAddress();

for (int i = 1; i <= 254; i++)
{
ip[3] = (byte)i;
InetAddress address = InetAddress.getByAddress(ip);
if (address.isReachable(1000))

for me. if you don't mind. I'm just novice with Java.