UDP Socket Programming - Domain Name System

// Datagram Sockets - DNS Server

// Server Program

import java.io.*;

import java.net.*;

public class DNS_Server

{

     public static void main(String as[]) throws IOException

     {

          DatagramSocket ds;

          DatagramPacket dp_send;

          DatagramPacket dp_rec;

         

          final int buf_size = 512;

          final int port = 1500;

         

          byte msg_rec[] = new byte[buf_size];

          byte msg_send[] = new byte[buf_size];

         

          try

          {

              ds = new DatagramSocket(port);

             

              dp_rec = new DatagramPacket(msg_rec, buf_size);

              ds.receive(dp_rec);

                  

              String dname = new String(dp_rec.getData()).trim();

             

              InetAddress ipaddr = InetAddress.getByName(dname);

             

              InetAddress DA = dp_rec.getAddress();

              int destport = dp_rec.getPort();

                 

              System.out.println(ipaddr); 

             

              msg_send = ipaddr.toString().getBytes();

            dp_send = new DatagramPacket(msg_send, msg_send.length, DA, destport);

              ds.send(dp_send);

             

          }

          catch(Exception e)

          {

              System.out.println("Exception " + e);

          }

     }

}

  

// Datagram Sockets - DNS Server

// Client Program

import java.io.*;

import java.net.*;

import java.util.*;

public class DNS_Client

{

     public static void main(String as[]) throws IOException

     {

          DatagramSocket ds;

          DatagramPacket dp_send;

          DatagramPacket dp_rec;

         

          final int port = 1500;

          final int buf_size = 512;

         

          Scanner s = new Scanner(System.in);

         

          byte[] msg_send = new byte[buf_size];    

          byte[] msg_rec = new byte[buf_size];

             

          try

          {

              ds = new DatagramSocket();

              System.out.print("Enter domain name : ");

              String data = s.nextLine();

             

              msg_send = data.getBytes();

              InetAddress DA = InetAddress.getByName("localhost");

             

              dp_send = new DatagramPacket(msg_send, msg_send.length, DA, port);

              ds.send(dp_send);

             

              dp_rec = new DatagramPacket(msg_rec, buf_size);

              ds.receive(dp_rec);

                  

              String ipaddr = new String(dp_rec.getData()).trim();

              System.out.println(ipaddr);

             

          }

          catch(Exception e)

          {

              System.out.println("Exception " + e);

          }

     }

}

           

             

                            

/*

Output 1

server window

     >javac DNS_Server.java

     >java DNS_Server

     www.drranurekha.com/160.153.137.167

client window

     >javac DNS_Client.java

     >java DNS_Client

     Enter domain name : www.drranurekha.com

     www.drranurekha.com/160.153.137.167

Output 2

server window

     >javac DNS_Server.java

     >java DNS_Server

     www.google.co.in/172.217.163.163

client window

     >javac DNS_Client.java

     >java DNS_Client

     Enter domain name : www.google.co.in

     www.google.co.in/172.217.163.163

*/