import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Server extends JFrame {
  private JTextField tf;
  private JTextArea display;
  private ObjectOutputStream output;
  private ObjectInputStream input;
  private ServerSocket server;
  private Socket connection;
  private int counter = 1;
  public Server(){
    super( "Server" );
    Container container = getContentPane();
    tf = new JTextField();
    tf.setEnabled( false );
    tf.addActionListener(new ActionListener() {
      public void actionPerformed( ActionEvent event )
      {
        sendData( event.getActionCommand() );
      }
    }); // end call to addActionListener
    container.add( tf, BorderLayout.NORTH );
    display = new JTextArea();
    container.add( new JScrollPane( display ),
                   BorderLayout.CENTER );
    setSize( 300, 150 );
    setVisible( true );
  }
  public void runServer(){
    try {
      server = new ServerSocket( 5000, 100 );
      while ( true ) {
        waitForConnection();
        getStreams();
        processConnection();
        closeConnection();
        ++counter;
      }
    }
    catch ( EOFException eofException ) {
      System.out.println( "Client terminated connection" );
    }
    catch ( IOException ioException ) {
      ioException.printStackTrace();
    }
  }
  private void waitForConnection() throws IOException{
    display.setText( "Waiting for connection\n" );
    connection = server.accept();
    display.append( "Connection " + counter +" received from: " +connection.getInetAddress().getHostName() );
  }
  private void getStreams() throws IOException{
    output = new ObjectOutputStream(connection.getOutputStream() );
    output.flush();
    input = new ObjectInputStream(connection.getInputStream() );
    display.append( "\nGot I/O streams\n" );
  }
  private void processConnection() throws IOException{
    String message = "SERVER>>> Connection successful";
    output.writeObject( message );
    output.flush();
    tf.setEnabled( true );
    do {
      try {
        message = ( String ) input.readObject();
        display.append( "\n" + message );
        display.setCaretPosition(display.getText().length() );
      }
      catch ( ClassNotFoundException classNotFoundException ) {
        display.append( "\nUnknown object type received" );
      }
    }
    while ( !message.equals( "CLIENT>>> TERMINATE" ) );
  }
  private void closeConnection() throws IOException{
    display.append( "\nUser terminated connection" );
    tf.setEnabled( false );
    output.close();
    input.close();
    connection.close();
  }
  private void sendData( String message ){
    try {
      output.writeObject( "SERVER>>> " + message );
      output.flush();
      display.append( "\nSERVER>>>" + message );
    }
    catch ( IOException ioException ) {
      display.append( "\nError writing object" );
    }
  }
  public static void main( String args[] ){
    Server application = new Server();
    application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE );
    application.runServer();
  }
}