Code Listing: Number Server

import java.io.*;
import java.net.*;
import java.lang.*;
 
public class NumberServer
{
     public static void main(String args[])
     {
       DatagramSocket receiveSocket = null;
       try
       {
         byte[] receiveBytes = new byte[1];
         InetAddress receiveAddr = InetAddress.getByName("localhost");
         int receivePort = 9000;
 
         receiveSocket = new DatagramSocket(receivePort, receiveAddr);
     
         while (true)
         {
           DatagramPacket receivePacket = new DatagramPacket(receiveBytes,               receiveBytes.length);
           receiveSocket.receive(receivePacket);
           String data = new String(receivePacket.getData(), 0,               receivePacket.getLength());
           byte[] reply = receivePacket.getData();
           String replyString = new String(reply);
           if (replyString.equals("4"))
               sendResultsBack(true, receivePacket.getAddress());
           else
               sendResultsBack(false, receivePacket.getAddress());
        }
       }
       catch (Exception e)
       {
          System.err.println("Exception " + e);
       }
       finally
       {
         if (receiveSocket != null)
         {
           try
           {
              receiveSocket.close();
           }
           catch (Exception e)
           {
             System.err.println("Exception " + e);
           }
         }
       }
     }
   
     // Send results back to the phone on port 9001
     public static void sendResultsBack(boolean rightanswer, InetAddress        sendAddr)
     {
       byte results[] = new byte[1];
       if (rightanswer)
         results[0] = (byte)'Y';
       else
         results[0] = (byte)'N';
       DatagramSocket sendSocket = null;
       int sendPort = 9001;
       try
       {
          sendSocket = new DatagramSocket();
          DatagramPacket sendPacket = new DatagramPacket(results,1, sendAddr,              sendPort);
          sendSocket.send(sendPacket);
       }
       catch (Exception e)
       {
         System.out.println("Exception " + e);
       }
       finally
       {
         if (sendSocket != null)
         {
           try
           {
              sendSocket.close();
           }
           catch (Exception e)
           {
             System.err.println("Exception " + e);
           }
         }
       }
     }
}