RARPServer.java

import java.net.*;
import java.util.HashMap;

public class RARPServer {
    public static void main(String[] args) throws Exception {
        DatagramSocket ds = new DatagramSocket(9092);
        HashMap<String, String> rarpTable = new HashMap<>();
        // Sample RARP Table: MAC -> IP
        rarpTable.put("00:11:22:33:44:55", "192.168.1.1");
        rarpTable.put("AA:BB:CC:DD:EE:FF", "192.168.1.2");
        rarpTable.put("11:22:33:44:55:66", "192.168.1.3");

        System.out.println("RARP Server running...");

        while (true) {
            byte[] buf = new byte[1024];
            DatagramPacket dp = new DatagramPacket(buf, buf.length);
            ds.receive(dp);

            String request = new String(dp.getData(), 0, dp.getLength());
            if (request.startsWith("REQUEST:")) {
                String mac = request.substring(8);
                String ip = rarpTable.getOrDefault(mac, "Not Found");
                byte[] reply = ("REPLY: IP for " + mac + " is " + ip).getBytes();
                ds.send(new DatagramPacket(reply, reply.length, dp.getAddress(), dp.getPort()));
                System.out.println("Sent reply for " + mac + ": " + ip);
            }
        }
    }
}