Server/Client streams

// Fig. 28.5: Client.java
// Client portion of a stream-socket connection between client and 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("");
            } 
         } 
      ); 

      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
   }

   // 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
      } 
      catch (EOFException eofException) 
      {
         displayMessage("\nClient terminated connection");
      } 
      catch (IOException ioException) 
      {
         ioException.printStackTrace();
      } 
      finally 
      {
         closeConnection(); // close connection
      }
   }

   // 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());
   }

   // 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");
   }

   // 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
         } 
         catch (ClassNotFoundException classNotFoundException) 
         {
            displayMessage("\nUnknown object type received");
         } 

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

   // 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
      } 
      catch (IOException ioException) 
      {
         ioException.printStackTrace();
      } 
   }

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

   // 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);
            }
         }  
      ); 
   } 

   // 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);
            }
         } 
      ); 
   } 

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

      // if no command line args
      if (args.length == 0)
         application = new Client("127.0.0.1"); // connect to localhost
      else
         application = new Client(args[0]); // use args to connect

      application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      application.runClient(); // run client application
   } 

} 

// Fig. 28.3: Server.java
// Server portion of a client/server stream-socket 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("");
            } 
         } 
      ); 

      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
   }

   // 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
            } 
            catch (EOFException eofException) 
            {
               displayMessage("\nServer terminated connection");
            } 
            finally 
            {
               closeConnection(); //  close connection
               ++counter;
            } 
         } 
      } 
      catch (IOException ioException) 
      {
         ioException.printStackTrace();
      } 
   }

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

   // 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");
   }

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

      // 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); // display message
         } 
         catch (ClassNotFoundException classNotFoundException) 
         {
            displayMessage("\nUnknown object type received");
         } 

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

   // 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
      } 
      catch (IOException ioException) 
      {
         ioException.printStackTrace();
      } 
   }

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

   // 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
            } 
         } 
      ); 
   } 

   // 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);
            } 
         } 
      ); 
   } 

   public static void main(String[] args)
   {
      Server application = new Server(); // create server
      application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      application.runServer(); // run server application
   } 

}