multichat.java

java3D game engine design of the source [three-dimensionalvirtualrealitynetworkprogram] - "virtual

// MultiChat.java
// Andrew Davison, June 2003, [e-mail]

/* A client for a multicast chat group which uses
   a NameServer for certain tasks.

   The NameServer does a very simplistic check of the
   user before the multicast group address is revealed.

   The NameServer answer's "who" questions.

   There are three possible types of message sent to the
   NameServer:
       hi <name>   // add the name to the NameServer
                      Get back the multicast address, or "no"

       bye <name>  // delete this name from the NameServer

       who         // send back a list of all the current members


   Types of message sent to the multicast group:

      (name): msg [ / toName ]

   A "/ toName" extension means that the message will only
   appear in the sender's text window and toName's window.
*/

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;


public class MultiChat extends JFrame 
                             implements ActionListener
{
  private static final int TIME_OUT = 5000;   // 5 secs
     // timeout used when waiting in receive()
  private static final int PACKET_SIZE = 1024;  // max size of a message

  // NameServer address and port constants
  private static final String SERVER_HOST = "localhost";
  private static final int SERVER_PORT = 1234;

  /* The multicast port. The multicast group address is
     obtained from the NameServer object. */
  private static final int GROUP_PORT = 5555;

  // for communication with the NameServer
  private DatagramSocket clientSock;
  private InetAddress serverAddr;

  // for communication with the multicast group
  private MulticastSocket groupSock;
  private InetAddress groupAddr;

  private String userName;   // name of this client

  private JTextArea jtaMesgs;
  private JTextField jtfMsg;
  private JButton jbWho;


  public MultiChat(String nm)
  {
     super( "Multicasting Chat Client for " + nm);
     userName = nm;
     initializeGUI();

     /* Attempt to register name and get multicast group 
        address from the NameServer */
     makeClientSock();
     sendServerMessage("hi " + userName);  // say "hi" to NameServer
     checkHiResponse();

     // Connect to the multicast group; say hi to everyone
     joinChatGroup();
     sendPacket("hi");

     addWindowListener( new WindowAdapter() {
       public void windowClosing(WindowEvent e)
       { sayBye(); }   // say bye at termination time
     });

     setSize(300,450);
     show();

     waitForPackets();
  } // end of MultiChat();


  // ----------- GUI related -------------------------


  private void initializeGUI()
  /* Text area in center, and controls below.
     Controls:
         - textfield for entering messages
         - a "Who" button
  */
  { Container c = getContentPane();
    c.setLayout( new BorderLayout() );

    jtaMesgs = new JTextArea(7, 7);
    jtaMesgs.setEditable(false);
    JScrollPane jsp = new JScrollPane( jtaMesgs);
    c.add( jsp, "Center");

    JLabel jlMsg = new JLabel("Message: ");
    jtfMsg = new JTextField(15);
    jtfMsg.addActionListener(this);    // pressing enter triggers sending of userName/score

    jbWho = new JButton("Who");
    jbWho.addActionListener(this);

    JPanel p1 = new JPanel( new FlowLayout() );
    p1.add(jlMsg); p1.add(jtfMsg);

    JPanel p2 = new JPanel( new FlowLayout() );
    p2.add(jbWho);

    JPanel p = new JPanel();
    p.setLayout( new BoxLayout(p, BoxLayout.Y_AXIS));
    p.add(p1); p.add(p2);

    c.add(p, "South");
  }  // end of initializeGUI()



  public void actionPerformed(ActionEvent e)
  /* Either a message is to be sent or the "Who"
     button has been pressed */
  {
    if (e.getSource() == jbWho)
      doWho();
    else if (e.getSource() == jtfMsg)
      sendMessage();
  }


  synchronized private void showMsg(String msg)
  /* Synchronized since this method can be called by the GUI 
     and application threads. */
  { jtaMesgs.append(msg);  }



  // ----------- NameServer communication methods --------------

  private void makeClientSock()
  {
    try {   // try to create the client's socket
      clientSock = new DatagramSocket();
      clientSock.setSoTimeout(TIME_OUT);  // include a time-out
    }
    catch( SocketException se ) {
      se.printStackTrace();
      System.exit(1);
    }

    try {  // NameServer address string --> IP no.
      serverAddr = InetAddress.getByName(SERVER_HOST);
    }
    catch( UnknownHostException uhe) {
      uhe.printStackTrace();
      System.exit(1);
    }
  }  // end of makeClientSock()


  private void checkHiResponse()
  /* The response to "hi <name>" can be the multicast group 
     address (in string form), or "no".
  */
  {
    String hiResponse = readServerMessage();

    if (hiResponse.equals("no")) {
      System.out.println("Login rejected; exiting...");
      System.exit(0);
    }
    else {
      try {  // multicast address string  --> IP no.
        groupAddr = InetAddress.getByName(hiResponse); 
      }       
      catch(Exception e)
      {  System.out.println(e);  
         System.exit(0);
      }
    }
  }  // end of checkHiResponse()


  private void doWho()
  /* Ask the NameServer who is currently registered with it. 
     Wait for the response and display it. */
  {
    sendServerMessage("who");
    String whoResponse = readServerMessage();
    if (whoResponse == null)
      showMsg("NameServer problem: no who info available\n");
    else
      showMsg(whoResponse);
  }  // end of doWho()


  private void sayBye()
  // Say bye to the multicast group *and* the NameServer
  {
    try {
      sendPacket("bye");    // "bye" to group
      sendServerMessage("bye " + userName);  // "bye" to server
    }
    catch(Exception e)
    {  System.out.println( e );  }

    System.exit( 0 ); 
  } // end of sayBye()


  private void sendServerMessage(String msg)
  // Send message to NameServer
  {
    try {
      DatagramPacket sendPacket =
          new DatagramPacket( msg.getBytes(), msg.length(), 
   						serverAddr, SERVER_PORT);
      clientSock.send( sendPacket );
    }
    catch(IOException ioe)
    {  System.out.println(ioe);  }
  } // end of sendServerMessage()


  private String readServerMessage()
  /* Read a message sent from the NameServer (when
     it arrives). There is a time-out associated with receive() */
  {
    String msg = null;
    try {
      byte[] data = new byte[PACKET_SIZE];
      DatagramPacket receivePacket = new DatagramPacket(data, data.length);

      clientSock.receive( receivePacket );  // wait for a packet
      msg = new String( receivePacket.getData(), 0,
                           receivePacket.getLength() );
    }
    catch(IOException ioe)
    {  System.out.println(ioe);  }

    return msg;
  }  // end of readServerMessage()



  // ----------------------- multicast group methods -------------
    
  private void joinChatGroup()
  {
    try {
      groupSock = new MulticastSocket(GROUP_PORT);
      groupSock.joinGroup(groupAddr);
    }
    catch(Exception e)
    {  System.out.println(e);  }
  }  // end of joinChatGroup()


  private void sendMessage()
  /* Check if the user has supplied a message, then
     send it to the multicast group. */
  {
    String msg = jtfMsg.getText().trim();
    // System.out.println("'"+msg+"'");

    if (msg.equals(""))
      JOptionPane.showMessageDialog( null, 
           "No message entered", "Send Message Error", 
			JOptionPane.ERROR_MESSAGE);
    else
      sendPacket(msg);
  }  // end of sendMessage()



  private void sendPacket(String msg)
  /* Send a packet to the multicast group. 
     Messages have the form 
				(name): msg
  */
  { String labelledMsg = "(" + userName + "): " + msg;
    try {
      DatagramPacket sendPacket = 
        new DatagramPacket(labelledMsg.getBytes(), labelledMsg.length(), 
										groupAddr, GROUP_PORT);          
      groupSock.send(sendPacket); 
    }
    catch(IOException ioe)
    {  System.out.println(ioe);  }
  }  // end of sendPacket()



  // --------------------------------------------------------
  // Processing of group messages by the application thread


  private void waitForPackets()
  /* Repeatedly receive a packet from the group, process it. 
     No messages are sent from here. Output is
     done from the GUI thread by calling sendPacket(). */
  {
    DatagramPacket packet;
    byte data[];

    try {
      while (true) {
        data = new byte[PACKET_SIZE];    // set up an empty packet
        packet = new DatagramPacket(data, data.length);
        groupSock.receive(packet);  // wait for a packet
        processPacket(packet);
      }
    }
    catch(IOException ioe)
    {  System.out.println(ioe);  }
  }  // end of waitForPackets()



   private void processPacket(DatagramPacket dp)
   /* Extract details from the received packet.
      Format:   (fromName): msg [ / toName ]

      A "/ toName" extension means that the message will only
      appear in the sender's text window and toName's window.
   */
   {
     String msg = new String( dp.getData(), 0, dp.getLength() );
     if (isVisibleMsg(msg, userName))
       showMsg(msg + "\n");
  }  // end of processPacket()



  private boolean isVisibleMsg(String msg, String name)
  /* A message is visible if it has no "/ name" part, or 
     "/ name" is the user, or the message is _from_ the user.
  */
  {
    int index = msg.indexOf("/");
    if (index == -1)  // no '/', so message is public
      return true;

    // does have a "/ name" part
    String toName = msg.substring(index+1).trim();
    if (toName.equals(name))  // for this user
      return true;
    else {   // for another user
      if (msg.startsWith("("+name))   // but from this user
        return true;
      else     // from someone else
        return false;
    }
  }  // end of isVisibleMsg()



  // ------------------------------------

  public static void main(String args[]) 
  {  
     if (args.length != 1) {
       System.out.println("usage:  java MultiChat <your userName>");
       System.exit(0);
     }
     new MultiChat(args[0]);  
  } // end of main()

} // end of MultiChat class