echoservermidlet.java

Bluetooth echo between pc server and client

// EchoServerMIDlet.java
// Andrew Davison, [e-mail], August 2005 

/* The MIDlet starts the echo server.
   It displays the current number of handlers, and a
   scrollable text box of messages that it has received.

   Pressing the "exit" command causes the server and its handlers
   to terminate.
*/

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;


public final class EchoServerMIDlet extends MIDlet 
                                  implements CommandListener 
{
  private Display display;
  private Form form;
  private StringItem numHandlersSI, messageSI;
  private ScrollableMessagesBox scroller;
  private Command exitCmd;

  private EchoServer echoServer;  // the top-level echo server
  private int numHandlers = 0;   // number of threaded echo handlers


  public EchoServerMIDlet() 
  {
    // build GUI
    form = new Form("Bluetooth Echo Server");
    int width = form.getWidth();
    int height = form.getHeight();

    numHandlersSI = new StringItem("No. Handlers: ", "0");
    form.append(numHandlersSI);
    int strHeight = numHandlersSI.getPreferredHeight();    // height of string item

    scroller = new ScrollableMessagesBox("Received Messages:", 
                                          width, height-strHeight-20);
                            // 20 is for the title and a bit of space
    form.append(scroller);

    exitCmd = new Command("Exit", Command.EXIT, 1);
    form.addCommand(exitCmd);
    form.setCommandListener(this);
  } // end of EchoServerMIDlet()


  protected void startApp() 
  {  
    display = Display.getDisplay(this);
    display.setCurrent(form);
    echoServer = new EchoServer(this);   // create the echo server
    echoServer.start();   // start it listening for connections
  } // end of startApp()


  protected void destroyApp(boolean unconditional) 
  { notifyDestroyed(); }

  protected void pauseApp() {}


  public void commandAction(Command c, Displayable d) 
  { if (c == exitCmd) {
      echoServer.closeDown();  // close down the server (and its handlers)
      destroyApp(true);
    }
  }


  // -------------- methods called by the handlers -----------------

  synchronized public void incrCount()
  // called when a new handler is created
  { numHandlers++;
    numHandlersSI.setText("" + numHandlers);
  }

  synchronized public void decrCount()
  // called when a handler is about to terminate
  { numHandlers--;
    numHandlersSI.setText("" + numHandlers);
  }

  synchronized public void showMessage(String msg)
  // used to show the message received by a handler
  { scroller.addMessage(msg); }

} // end of EchoServerMIDlet class