client.java

基于网络的CS聊天程序,对于想学点网络编程的知识的同志很有帮助

// Fig. 17.5: Client.java
// Set up a Client that will read information sent
// from a Server and display the information.

// 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 ObjectOutputStream output;
   private ObjectInputStream input;
   private String message = "";
   private String chatServer;
   private Socket client;

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

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

      Container container = getContentPane();

      // create enterField and register listener
      enterField = new JTextField();
      enterField.setEnabled( false );

      enterField.addActionListener(

         new ActionListener() {

            // send message to server
            public void actionPerformed( ActionEvent event )
            {
               sendData( event.getActionCommand() );
             
            }

         }  // end anonymous inner class

      ); // end call to addActionListener

      container.add( enterField, BorderLayout.NORTH );

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

      setSize( 300, 150 );
      setVisible( true );
   }

   // connect to server and process messages from server
   public void runClient() 
   {
      // connect to server, get streams, process connection
      try {

         // Step 1: Create a Socket to make connection
         connectToServer();

         // Step 2: Get the input and output streams
         getStreams();

         // Step 3: Process connection
         processConnection();

         // Step 4: Close connection
         closeConnection();
      }

      // server closed connection
      catch ( EOFException eofException ) {
         System.out.println( "Server terminated connection" );
      }

      // process problems communicating with server
      catch ( IOException ioException ) {
         ioException.printStackTrace();
      }
   }

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

      // flush output buffer to send header information
      output.flush();

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

      displayArea.append( "\nGot I/O streams\n" );
   }

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

      // create Socket to make connection to server
      client = new Socket( 
         InetAddress.getByName( chatServer ), 5000 );

      // display connection information
      displayArea.append( "Connected to: " +
         client.getInetAddress().getHostName() );
   }

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

      // process messages sent from server
      do {

         // read message and display it
         try {
            message = ( String ) input.readObject();
            displayArea.append( "\n" + message );
            displayArea.setCaretPosition(
               displayArea.getText().length() );
         }

         // catch problems reading from server
         catch ( ClassNotFoundException classNotFoundException ) {
            displayArea.append( "\nUnknown object type received" );
         }

      } while ( !message.equals( "SERVER>>> TERMINATE" ) );

   }  // end method process connection

   // close streams and socket
   private void closeConnection() throws IOException
   {
      displayArea.append( "\nClosing connection" );
      output.close();
      input.close();
      client.close();
   }

   // send message to server
   private void sendData( String message )
   {
      // send object to server
      try {
         output.writeObject( "CLIENT>>> " + message );
         output.flush();
         displayArea.append( "\nCLIENT>>>" + message );
      }

      // process problems sending object
      catch ( IOException ioException ) {
         displayArea.append( "\nError writing object" );
      }
   }

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

      if ( args.length == 0 )
         application = new Client( "127.0.0.1" );
      else
         application = new Client( args[ 0 ] );

      application.setDefaultCloseOperation(
         JFrame.EXIT_ON_CLOSE );

      application.runClient();
   }

}  // end class Client

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