client.java

Messenger Client Java

// Fig. 24.7: Client.java
// Client that reads and displays information sent from a Server.
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 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 Client extends JFrame 
{
   private JTextField enterField; // enters information from user
   private JTextArea displayArea; // display information to user
   private ObjectOutputStream output; // output stream to server
   private ObjectInputStream input; // input stream from server
   private String message = ""; // message from server
   private String chatServer; // host server for this application
   private Socket client; // socket to communicate with server

   // initialize chatServer and set up GUI
   public Client( String host )
   {
      super( "Client" );

      chatServer = host; // set server to which this client connects

      enterField = new JTextField(); // create enterField
      enterField.setEditable( false );
      enterField.addActionListener(
         new ActionListener() 
         {
            // send message to server
            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 Client constructor

   // connect to server and process messages from server
   public void runClient() 
   {
      try // connect to server, get streams, process connection
      {
         connectToServer(); // create a Socket to make connection
         getStreams(); // get the input and output streams
         processConnection(); // process connection
      } // end try
      catch ( EOFException eofException ) 
      {
         displayMessage( "\nClient terminated connection" );
      } // end catch
      catch ( IOException ioException ) 
      {
         ioException.printStackTrace();
      } // end catch
      finally 
      {
         closeConnection(); // close connection
      } // end finally
   } // end method runClient

   // connect to server
   private void connectToServer() throws IOException
   {      
      displayMessage( "Attempting connection\n" );

      // create Socket to make connection to server
      client = new Socket( InetAddress.getByName( chatServer ), 12345 );

      // display connection information
      displayMessage( "Connected to: " + 
         client.getInetAddress().getHostName() );
   } // end method connectToServer

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

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

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

   // process connection with server
   private void processConnection() throws IOException
   {
      // enable enterField so client user can send messages
      setTextFieldEditable( true );

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

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

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

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

   // send message to server
   private void sendData( String message )
   {
      try // send object to server
      {
         output.writeObject( InetAddress.getLocalHost().getHostName()+" >>> " + message );
         output.flush(); // flush data to output
         displayMessage( "\n"+ InetAddress.getLocalHost().getHostName()+" >>> " + 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 );
            } // 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 anonymous inner class
      ); // end call to SwingUtilities.invokeLater
   } // end method setTextFieldEditable
} // end class Client

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