// Fig. 17.7: Client.java
// Set up a Client that will send packets to a
// server and receive packets from a server.

// Java core packages
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;

// Java extension packages
import javax.swing.*;

public class Client extends JFrame {
   private JTextField enterField;
   private JTextArea displayArea;
   private DatagramPacket sendPacket, receivePacket;
   private DatagramSocket socket;

   // set up GUI and DatagramSocket
   public Client()
   {
      super( "Client" );

      Container container = getContentPane();

      enterField = new JTextField( "Type message here" );

      enterField.addActionListener(

         new ActionListener() {

            // create and send a packet
            public void actionPerformed( ActionEvent event )
            {
               // create and send packet
               try {
                  displayArea.append( 
                     "\nSending packet containing: " +
                     event.getActionCommand() + "\n" );

                  // get message from textfield and convert to 
                  // array of bytes
                  String message = event.getActionCommand();
                  byte data[] = message.getBytes();
         
                  // create sendPacket
                  sendPacket = new DatagramPacket( 
                     data, data.length,
                     InetAddress.getLocalHost(), 5000 );

                  // send packet
                  socket.send( sendPacket );

                  displayArea.append( "Packet sent\n" );
                  displayArea.setCaretPosition(
                     displayArea.getText().length() );
               }

               // process problems creating or sending packet
               catch ( IOException ioException ) {
                  displayArea.append( 
                     ioException.toString() + "\n" );
                  ioException.printStackTrace();
               }

            }  // end actionPerformed

         }  // end anonymous inner class

      ); // end call to addActionListener

      container.add( enterField, BorderLayout.NORTH );

      displayArea = new JTextArea();
      container.add( new JScrollPane( displayArea ),
         BorderLayout.CENTER );

      setSize( 400, 300 );
      setVisible( true );

      // create DatagramSocket for sending and receiving packets
      try {
         socket = new DatagramSocket();
      }

      // catch problems creating DatagramSocket
      catch( SocketException socketException ) {
         socketException.printStackTrace();
         System.exit( 1 );
      }

   }  // end Client constructor

   // wait for packets to arrive from Server, 
   // then display packet contents
   public void waitForPackets()
   {
      // loop forever
      while ( true ) {

         // receive packet and display contents
         try {

            // set up packet
            byte data[] = new byte[ 100 ];
            receivePacket = 
               new DatagramPacket( data, data.length );

            // wait for packet
            socket.receive( receivePacket );
 
            // display packet contents
            displayPacket();
         }
 
         // process problems receiving or displaying packet
         catch( IOException exception ) {
            displayArea.append( exception.toString() + "\n" );
            exception.printStackTrace();
         }

      }  // end while

   }  // end method waitForPackets

   // display contents of receivePacket
   private void displayPacket()
   {
      displayArea.append( "\nPacket received:" +
         "\nFrom host: " + receivePacket.getAddress() +
         "\nHost port: " + receivePacket.getPort() +
         "\nLength: " + receivePacket.getLength() +
         "\nContaining:\n\t" +
         new String( receivePacket.getData(), 0,
            receivePacket.getLength() ) );

      displayArea.setCaretPosition(
         displayArea.getText().length() );
   }

   // execute application
   public static void main( String args[] )
   {
      Client application = new Client();

      application.setDefaultCloseOperation( 
         JFrame.EXIT_ON_CLOSE );

      application.waitForPackets();
   }

}  // end class Client


/**************************************************************************
 * (C) Copyright 2002 by Deitel & Associates, Inc. and Prentice Hall.     *
 * All Rights Reserved.                                                   *
 *                                                                        *
 * DISCLAIMER: The authors and publisher of this book have used their     *
 * best efforts in preparing the book. These efforts include the          *
 * development, research, and testing of the theories and programs        *
 * to determine their effectiveness. The authors and publisher make       *
 * no warranty of any kind, expressed or implied, with regard to these    *
 * programs or to the documentation contained in these books. The authors *
 * and publisher shall not be liable in any event for incidental or       *
 * consequential damages in connection with, or arising out of, the       *
 * furnishing, performance, or use of these programs.                     *
 *************************************************************************/