wireless messaging api in j2me

dear every one , i am in critical state , i had to write a application
that can send and receive sms in the same application i am able to
send the sms ( got the java file from the book ) i ahve written an
another application to recive the sms in the same application but
program is not executing , it says that their is some excetion in
startApp fuction , my boss needs it uergently , iahve trusted this
group since my college days and i have laways got the solution to my
problem kindly help me out

here the source code i have written to recive sms in application ,
first i have send the sms "hello" to my mobile the i want to recive it
on the same

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.wireless.messaging.*;
import javax.microedition.io.*;

public class main extends MIDlet implements CommandListener,Runnable {

    Sender give;
    String mPort="50000";
    String msgReceived = null;
    private MessageConnection conn = null;
    private boolean mEndNow = false;
    Thread reciver = null;
    Form mForm,reciveForm;
    Command ok;
    Command Exit;
    public void startApp() {
        mForm = new Form( "Hello");
        mForm.append("hello virtu");
        ok = new Command("ok",Command.OK,0);
        Exit = new Command("Exit",Command.EXIT,0);
        mForm.addCommand(ok);
        mForm.addCommand(Exit);
        mForm.setCommandListener(this);
        Display mDisplay = null;
        mDisplay.getCurrent();
        mDisplay.setCurrent(mForm);

// give.sendMsg("9990753070","5000" ,"hello" );

    }

    public void pauseApp() {
    }

    public void destroyApp(boolean unconditional) {

    }
    public void commandAction(Command c , Displayable d)
    {
        if (c == ok)
        {
            give.sendMsg("9990753070","5000" ,"hello" );
              reciver.start();
        }
    }
    public void run()
    {
        Message msg = null;
        String msgReceived = null;
        conn=null;
        mEndNow = false ;
        /** Check for sms connection **/
          try{
               conn = (MessageConnection) Connector.open("sms://:" +
mPort);
               msg = conn.receive();
               while(msg !=null)
               {
                   if(msg instanceof TextMessage)
                   {
                       msgReceived = ((TextMessage)msg).getPayloadText
();

                       Display vDisplay = null;
                       reciveForm = new Form (" msg Arrived");
                       reciveForm.append(msgReceived);
                       vDisplay.getCurrent();
                       vDisplay.setCurrent(mForm);

                   }
               }
          }
          catch(Exception e)
          {

          }

        }

    }

relpy me as soon as possible