// Set up a server that will receive a connection froma client, send
// a string to the client, and close the connection.
import java.io.EOFException;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class Server extends JFrame
{
private JTextField enterField; // inputs message from user
private JTextArea displayArea; // display information to user
private ObjectOutputStream output; // output stream to client
private ObjectInputStream input; // input stream from client
private ServerSocket server; // server socket
private Socket connection; // connection to client
private int counter = 1; // counter of number of connections

// set up GUI
public Server()
{
super( "Server" );

enterField = new JTextField(); // create enterField
enterField.setEditable( false );
enterField.addActionListener(
new ActionListener()
{
// send message to client
public void actionPerformed( ActionEvent event )
{
sendData( event.getActionCommand() );
enterField.setText( "" );
} // end method actionPerformed
} // end anonymous inner class
); // end call to addActionListener

add( enterField, BorderLayout.NORTH );

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

setSize( 300, 150 ); // set size of window
setVisible( true ); // show window
} // end Server constructor

// set up and run server
public void runServer()
{
try // set up server to receive connections; process connections
{
server = new ServerSocket( 12345, 100 ); // create ServerSocket

while ( true )
{
try
{
waitForConnection(); // wait for a connection
getStreams(); // get input & output streams
processConnection(); // process connection
} // end try
catch ( EOFException eofException )
{
displayMessage( "\nServer terminated connection" );
} // end catch
finally
{
closeConnection(); // close connection
counter++;
} // end finally
} // end while
} // end try
catch ( IOException ioException )
{
ioException.printStackTrace();
} // end catch
} // end method runServer

// wait for connection to arrive, then display connection info
private void waitForConnection() throws IOException
{
displayMessage( "Waiting for connection\n" );
connection = server.accept(); // allow server toaccept connection
displayMessage( "Connection " + counter + " received from: " +
connection.getInetAddress().getHostName() );
} // end method waitForConnection

// get streams to send and receive data
private void getStreams() throws IOException
{
// set up output stream for objects
output = new ObjectOutputStream( connection.getOutputStream() );
output.flush(); // flush output buffer to send header information

// set up input stream for objects
input = new ObjectInputStream( connection.getInputStream() );

displayMessage( "\nGot I/O streams\n" );
} // end method getStreams

// process connection with client
private void processConnection() throws IOException
{
String message = "Connection successful";
sendData( message ); // send connection successfulmessage

// enable enterField so server user can send messages
setTextFieldEditable( true );

do // process messages sent from client
{
try // read message and display it
{
message = ( String ) input.readObject(); //read new message
displayMessage( "\n" + message ); // displaymessage
} // end try
catch ( ClassNotFoundException classNotFoundException )
{
displayMessage( "\nUnknown object type received" );
} // end catch

} while ( !message.equals( "CLIENT>>> TERMINATE"));
} // end method processConnection

// close streams and socket
private void closeConnection()
{
displayMessage( "\nTerminating connection\n" );
setTextFieldEditable( false ); // disable enterField

try
{
output.close(); // close output stream
input.close(); // close input stream
connection.close(); // close socket
} // end try
catch ( IOException ioException )
{
ioException.printStackTrace();
} // end catch
} // end method closeConnection

// send message to client
private void sendData( String message )
{
try // send object to client
{
output.writeObject( "SERVER>>> " + message );
output.flush(); // flush output to client
displayMessage( "\nSERVER>>> " + message );
} // end try
catch ( IOException ioException )
{
displayArea.append( "\nError writing object");
} // end catch
} // end method sendData

// manipulates displayArea in the event-dispatch thread
private void displayMessage( final String messageToDisplay )
{
SwingUtilities.invokeLater(
new Runnable()
{
public void run() // updates displayArea
{
displayArea.append( messageToDisplay );// append message
} // end method run
} // end anonymous inner class
); // end call to SwingUtilities.invokeLater
} // end method displayMessage

// manipulates enterField in the event-dispatch thread
private void setTextFieldEditable( final boolean editable )
{
SwingUtilities.invokeLater(
new Runnable()
{
public void run() // sets enterField's editability
{
enterField.setEditable( editable );
} // end method run
} // end inner class
); // end call to SwingUtilities.invokeLater
} // end method setTextFieldEditable
       public static void main( String args[] )
       {
          Server application = new Server(); // create server
         application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
         application.runServer(); // run server application
      } // end main
} // end class Server
