SimpleARP.java

import java.util.*;

public class SimpleARP {
    public static void main(String[] args) {
        HashMap<String, String> arpTable = new HashMap<>();
        Scanner sc = new Scanner(System.in);
        
        // Pre-populate some entries
        arpTable.put("192.168.1.1", "AA:BB:CC:DD:EE:01");
        arpTable.put("192.168.1.2", "AA:BB:CC:DD:EE:02");
        
        System.out.println("ARP PROTOCOL DEMO");
        System.out.println("==================");
        
        System.out.print("Enter IP address to resolve: ");
        String ip = sc.nextLine();
        
        // ARP Resolution
        System.out.println("\nARP Request: Who has " + ip + "?");
        
        if (arpTable.containsKey(ip)) {
            String mac = arpTable.get(ip);
            System.out.println("ARP Reply: " + ip + " is at " + mac);
            System.out.println("\nData can be sent to MAC: " + mac);
        } else {
            System.out.println("No ARP reply received - Host unreachable!");
        }
        
        // Display ARP Table
        System.out.println("\nCurrent ARP Table:");
        System.out.println("IP\t\t\tMAC");
        for (Map.Entry<String, String> e : arpTable.entrySet()) {
            System.out.println(e.getKey() + "\t\t" + e.getValue());
        }
        
        sc.close();
    }
}