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 */
package chapter2;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

/** *
 * Server that echoes back client's messages.
 * At end of dialogue, sends message indicating number of
 * messages received. Uses datagrams.
 *
 * @author jeffrey
 */
public class UDPEchoServer
{

    private static final int PORT = 1234;
    private static DatagramSocket datagramSocket;
    private static DatagramPacket inPacket, outPacket;
    private static byte[] buffer;

    public static void main( String[] args )
    {
        System.out.println( "Opening port... \n" );

        try
        {
            datagramSocket = new DatagramSocket( PORT );                            // STEP 1
        }
        catch ( Exception e )
        {
            System.out.println( e.getMessage() );
            System.exit( 1 );
        }

        handleClient();
    }

    private static void handleClient()
    {
        try
        {
            String messageIn, messageOut;
            int numMessages = 0;

            do
            {
                buffer = new byte[256];                                             // STEP 2
                inPacket = new DatagramPacket( buffer, buffer.length );            // STEP 3
                datagramSocket.receive( inPacket );                                 // STEP 4

                InetAddress clientAddress = inPacket.getAddress();                  // STEP 5
                int clientPort = inPacket.getPort();                                // STEP 5

                messageIn = new String( inPacket.getData(), 0, inPacket.getLength() ); // STEP 6
                System.out.println( "Message received: " + messageIn );

                numMessages++;
                messageOut = "Message " + numMessages + ": " + messageIn;

                // STEP 7
                outPacket = new DatagramPacket( messageOut.getBytes(), messageOut.length(), clientAddress, clientPort );

                // STEP 8
                datagramSocket.send( outPacket );
            }
            while ( true );
        }
        catch ( Exception e )
        {
            e.printStackTrace();
        }
        finally
        {
            System.out.println( "\n* Closing connection... *" );
            datagramSocket.close();
        }
    }
}