Multithreading - Games problem

[raagaas]

I am working on a multiplayer game ....

Here is what the structure of my program(s) luks like ....

I have the BlueToothMidlet which implements Runnable .... creates server/connects to a server according to the choice provided .... as soon as the client and server are ready .... i do Display.getDisplay(this).setCurrent(MyGameCanvas) ....and the canvas does all the initial work each player needs to do .... after each player is done with his work ... he should tell the other player that he is done ....

now the run method of BlueToothMidlet is always running .... i created another thread (Thread t ) to send and receives messages from client/server..... and when i want to send/receive message i do "t.start()" so that each player knows that the other player is "done" ... but i am getting an "IllegalThreadStateException" in the BlueToothMidlet's run method ...everytime !!

Also i want to send messages as soon as each player is done with his turn to play ....

What might be the problem ??

[DevelopmentTeam]

This error is thrown usually when more than one thread is created and access the same variable. Also first make sure if there is only one bluetooth thread running everytime otherwise you need to make the other thread wait untill the first one finishes. Please let me know if you are testing on a device or emulator... if possible put your bluetooth code here...

[raagaas]

am using an emulator for now ....
Actually yes .... both the threads access the variable "sendStr" ....

i am posting the run() method of the BlueToothMidlet() ... the ClientServer class performs all the BlueTooth Connection(s) ... sending and receiving messages ....

Code: Select all

     public void run()
    {
       
       while (gameAlive)
       {
         try  {
            if (clientServerObj == null) {
               clientServerObj = new ClientServer();
               t = new Thread() {
                  public void run() {
                     clientServerObj.SendMessages(sendStr);
                      rcvStr = clientServerObj.RecieveMessages();
                     if (rcvStr.equals("CHANCE_DONE"))
                        remoteGameState = rcvStr;
                     return;
                  }
               };
               
               
               if (clientServerObj.isServerConnected()) {
                  if (myCanvas == null)
                     myCanvas = new MyGameCanvas(this, Display
                           .getDisplay(this));
                  Display.getDisplay(this).setCurrent(myCanvas);
                                 
               }
            }
            if (clientServerObj.isClientConnected()) {
               
               if (myCanvas == null)
                  bCanvas = new MyGameCanvas(this, Display
                        .getDisplay(this));
               Display.getDisplay(this).setCurrent(myCanvas);
               
            }

            
            if (myCanvas.getGameState() == "CHANCE_DONE") {
   
               sendStr = "CHANCE_DONE";
               
               waitPlayer.append("Waiting for other player....");
               Display.getDisplay(this).setCurrent(waitPlayer);
               
               myCanvas.setGameState("BEGIN_GAME");
            }
            if (myCanvas.getGameState() == "BEGIN_GAME"
                  && remoteGameState == "CHANCE_DONE") {
               System.out.println("Lets Begin the Game !!");
            }
            
            
            t.start();

         } catch (Exception ex) {
            ex.printStackTrace();
         }
      }
    }


[raagaas]

am eagerly waitin for the reply ...
is nebody thr ?

[DevelopmentTeam]

Better write a seperate class for bluetooth thread with runnable implementation. And make the function syncronized so that no 2 thread access the function at the same time.

[DevelopmentTeam]

For example see the httpconnection sample code here

[DevelopmentTeam]

the illegalstateexception will occur when you are redeclaring the same thread before the thread is ended...

[raagaas]

thanx .... i created another class like the one u showed in the above code and it worked ... yipppee

[DevelopmentTeam]

Always when you use Bluetooth/Httpconnection/file access/Any such device oriented operations make sure that you only have one thread doing the same operation, most devices dont allow 2 connections at the same time. So it is always safe to ensure this...