EchoClient to accompany EchoServer...

EchoClient.java

package uk.ac.qub.networking;

import java.io.EOFException;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.InetAddress;
import java.net.Socket;
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class EchoClient extends JFrame {

    private JTextField enterField;
    private JTextArea displayArea;
    private ObjectOutputStream output;
    private ObjectInputStream input;
    private String message = "";
    private String chatServer;
    private Socket client;
 
    public EchoClient ( String host) {
        super( "Client" );
        
        chatServer = host;
        
        enterField = new JTextField();
        enterField.setEditable( false );
        enterField.addActionListener(
            new ActionListener()
            {
                public void actionPerformed( ActionEvent event) {
                    sendData( event.getActionCommand() );
                    enterField.setText( "" );
                }
            }
        );
        
        add( enterField, BorderLayout.NORTH );
        
        displayArea = new JTextArea();
        add( new JScrollPane ( displayArea ), BorderLayout.CENTER );
        
        setSize( 600, 300);
        setVisible( true );
    }
    
    public void runClient() {
        try {
            connectToServer();
            getStreams();
            processConnection();
        }
        catch (IOException ioException)
        {
            ioException.printStackTrace();
        }
        finally
        {
            closeConnection();
        }
    }
    
    private void connectToServer() throws IOException {
        displayMessage( "Attempting connection\n" );
        
        client = new Socket( InetAddress.getByName( chatServer ), 12321 );
        
        displayMessage( "Connected to: "+
            client.getInetAddress().getHostName() );
    }
    
    private void getStreams() throws IOException {
        output = new ObjectOutputStream( client.getOutputStream() );
        output.flush();
        
        input = new ObjectInputStream( client.getInputStream() );
        
        displayMessage("\nGot I/O streams\n" );
    }
    
    private void processConnection() throws IOException {
        setTextFieldEditable( true );
        
        do {
            try {
                message = ( String ) input.readObject();
                displayMessage( "\n" + message );
            }
            catch ( ClassNotFoundException classNotFoundException )
            {
                displayMessage( "\nUnknown object type received" );
            }    
        } while ( !message.equals( "SERVER> TERMINATE"));
    }
    
    private void closeConnection() {
        displayMessage("\nClosing connection");
        setTextFieldEditable(false);
        
        try {
            output.close();
            input.close();
            client.close();
        }
        catch (IOException ioException) 
        {
            ioException.printStackTrace();
        }
    }
    
    private void sendData( String message ) {
        try {
            output.writeObject( "CLIENT>" + message);
            output.flush();
            displayMessage("\nCLIENT> " + message);
        }
        catch (IOException ioException) 
        {
            displayArea.append("\nError writing object");
         
        }
    }
    
    private void displayMessage( final String messageToDisplay ) {
        SwingUtilities.invokeLater(
            new Runnable() {
                public void run() {
                    displayArea.append( messageToDisplay);
                }
            }
        );
    }
    
    private void setTextFieldEditable( final boolean editable ) {
        SwingUtilities.invokeLater(
            new Runnable() {
                public void run() {
                    enterField.setEditable( editable );
                }
            }
        );
    }   
}