Question

Bluetooth J2ME - Need practical help with connection example

Asked by: idur

Hello, I am a newbe in J2ME and Bluetooth. I am trying to run an example I found on the net , but not successfull!! And I am getting frustrated because I need to establish a connection via bluetooth to access some data in a Data base!! Which would be the best connection type?? I am lost too because I didn´t find anywhere explaining where do I find the UUID?? neither the host neither the port in btspp://host:port;parameters.
Here is the example I am trying to run!!!
Note that I didn´t change the UUID and host and port because I don´t know!!! Maybe that´s because it´s not working??
When I execute it, it just opens a black screen with nothing. I am testing it on the Series 60 MIDP emulator of NOKIA. Can anyone help me!!!!!

If anyone has a connection via bluetooth with a data base, I would appreciate too!!

BluetoothMIDlet
=============================================================
import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import javax.bluetooth.*;

public class BluetoothMIDlet extends MIDlet implements Runnable, CommandListener {

public BluetoothMIDlet(){}

public void startApp() throws MIDletStateChangeException{
new Thread(this).start();
}

public void pauseApp(){}
public void destroyApp(boolean unconditional){}

public void run(){}
public void commandAction (Command c, Displayable d){
notifyDestroyed();}

}

=============================================================
HelloClient
=============================================================
import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import javax.bluetooth.*;

public class HelloClient extends BluetoothMIDlet {

public void run(){
Form f = new Form("Cliente");
f.addCommand(new Command("Sair", Command.EXIT,1));
f.setCommandListener(this);
Display.getDisplay(this).setCurrent(f);

try {
LocalDevice local = LocalDevice.getLocalDevice();
DiscoveryAgent agent = local.getDiscoveryAgent();
String connString = agent.selectService(
new UUID("86b4d249fb8844d6a756ec265dd1f6a3", false),
ServiceRecord.NOAUTHENTICATE_NOENCRYPT, false);

if (connString != null){
try{
StreamConnection conn = (StreamConnection)
Connector.open(connString);

OutputStream out = conn.openOutputStream();
out.write("Esta menssagem é de teste".getBytes());
out.close();
conn.close();

f.append("Menssagem enviada corretamente");

}
catch (IOException e){
f.append("IOException:" + e.getMessage());
}

}
else{

f.append("Não foi possivel localizar o servico");

}
}catch (BluetoothStateException e){
f.append("BluetoothStateException: ");
f.append(e.getMessage());
}
}
}

=============================================================
HelloServer
==============================================================
import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import javax.bluetooth.*;

public class HelloServer extends BluetoothMIDlet {

public void run(){

Form f = new Form("Servidor");
f.addCommand(new Command("Sair",Command.EXIT, 1));
f.setCommandListener(this);
Display.getDisplay(this).setCurrent(f);

try{
LocalDevice local = LocalDevice.getLocalDevice();
if (!local.setDiscoverable(DiscoveryAgent.GIAC)){
f.append("Falha ao mudar para modo Discoverable");
return;
}
StreamConnectionNotifier notifier = (StreamConnectionNotifier)
Connector.open("btspp://localhost:"+"86b4d249fb8844d6a756ec256dd1f6a3");

StreamConnection conn = notifier.acceptAndOpen();

InputStream in = conn.openInputStream();
ByteArrayOutputStream out = new ByteArrayOutputStream();

int data;
while ((data=in.read()) != -1) {
out.write(data);
}

f.append(out.toString());
in.close();
conn.close();
notifier.close();

}catch (BluetoothStateException e){
f.append("BluetoothStateException:"+e.getMessage());
}catch (IOException e){
f.append("IOException:"+e.getMessage());
}

}
}

==============================================================

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Asked On: 2004-05-06 at 17:15:45ID20980970
Tags: j2me
,; bluetooth
,; example
Topic: Wireless Technologies
Participating Experts: 2
Points: 50
Comments: 8

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Answers

by: jimmackPosted on 2004-05-07 at 00:43:02ID: 11012703

Before worrying about the details of Bluetooth, I would ensure that the MIDlets are displaying something useful so that you can begin debugging. You have shown the code for two MIDlets. How are you executing these? Are you running two emulators, one with the client and one with the server?

When you say "black screen", do you mean "blank screen"? Is there no Form title or exit command?

The most likely reason that nothing is being displayed is that your form is being displayed in the same thread that is attempting the bluetooth connection. If the connection is blocked, then the form probably won't be displayed. I would suggest that you modify the BluetoothMIDlet as follows:

public class BluetoothMIDlet extends MIDlet implements Runnable, CommandListener {
private Command exitCommand;

public BluetoothMIDlet(){
exitCommand = new Command("Sair", Command.EXIT, 1);
}

public void startApp() throws MIDletStateChangeException{
mainForm = new Form("???");
mainForm.addCommand(exitCommand);
mainForm.setCommandListener(this);
Display.getDisplay(this).setCurrent(mainForm);
new Thread(this).start();
}

public void pauseApp(){}
public void destroyApp(boolean unconditional){}

public void run(){}
public void commandAction (Command c, Displayable d){
if (c == exitCommand){
destroyApp(true);
notifyDestroyed();
}
}
}

This will display the form in the main thread, separately from the bluetooth connection attempt.

You'll also need to modify the client and server "run()" methods:

Client:
public void run(){
// Form f = new Form("Cliente");
// f.addCommand(new Command("Sair", Command.EXIT,1));
// f.setCommandListener(this);
// Display.getDisplay(this).setCurrent(f);

mainForm.setTitle("Cliente");

try {
LocalDevice local = LocalDevice.getLocalDevice();
.
.
.

Server:
public void run(){

// Form f = new Form("Servidor");
// f.addCommand(new Command("Sair",Command.EXIT, 1));
// f.setCommandListener(this);
// Display.getDisplay(this).setCurrent(f);

mainForm.setTitle("Servidor");

try{
LocalDevice local = LocalDevice.getLocalDevice();
.
.
.

When the display is working, you should get some more useful output :-)

by: idurPosted on 2004-05-07 at 05:49:42ID: 11014112

OK , I´ll try this later today. And I am running the server in one emulator and client in other...
I should put the BluetoohMIDlet with bothe client and server, right ????
Is the UUID correct?? Can you explai to me what exactly is it? and haw to set it up?? Is it aleatory??

by: idurPosted on 2004-05-07 at 18:32:54ID: 11019628

I changed it a little bit, but I still can´t make it work!!! Help!

I made two classes , one for client and one for Server and ran each one in a separate emulator.
The server throws an exeption saying that thare was a problem when setting the device to discoverable.
The client just changes the title to Cliente and shows (No data) in the middle of the screen.
This is just an example to send a message to another device, it´s very simple and I am not getting it to work....:(

Client
=============================================================
import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import javax.bluetooth.*;

public class BluetoothMIDletClient extends MIDlet implements Runnable, CommandListener {

      Form mainForm = new Form("???");
      private Command exitCommand;

public BluetoothMIDletClient(){
exitCommand = new Command("Sair", Command.EXIT, 1);
}

public void startApp() throws MIDletStateChangeException{

mainForm.addCommand(exitCommand);
mainForm.setCommandListener(this);
Display.getDisplay(this).setCurrent(mainForm);
new Thread(this).start();

}

public void pauseApp(){}
public void destroyApp(boolean unconditional){}

public void run(){
      System.out.println("Passou aqui");
      mainForm.setTitle("Cliente");

      try {
            LocalDevice local = LocalDevice.getLocalDevice();
            DiscoveryAgent agent = local.getDiscoveryAgent();
            String connString = agent.selectService(
                        new UUID("102030405060708090A0B0C0D0E0F010", false),
                        ServiceRecord.NOAUTHENTICATE_NOENCRYPT, false);
            System.out.print("String conexao:"+connString);
            if (connString != null){
                  try{
                        StreamConnection conn = (StreamConnection)
                        Connector.open(connString);

                        OutputStream out = conn.openOutputStream();
                        out.write("Esta menssagem é de teste".getBytes());
                        out.close();
                        conn.close();

                        mainForm.append("Menssagem enviada corretamente");

                  }
                  catch (IOException e){
                        mainForm.append("IOException:" + e.getMessage());
                  }

            }
            else{

                  mainForm.append("Não foi possivel localizar o servico");

            }
      }catch (BluetoothStateException e){
            mainForm.append("BluetoothStateException: ");
            mainForm.append(e.getMessage());
      }
}
public void commandAction (Command c, Displayable d){
if (c == exitCommand){
destroyApp(true);
notifyDestroyed();
}
}
}
=============
Server
===========================================================
import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import javax.bluetooth.*;

public class BluetoothMIDletServer extends MIDlet implements Runnable, CommandListener {

      Form mainForm = new Form("???");
      private Command exitCommand;

public BluetoothMIDletServer(){
exitCommand = new Command("Sair", Command.EXIT, 1);
}

public void startApp() throws MIDletStateChangeException{

mainForm.addCommand(exitCommand);
mainForm.setCommandListener(this);
Display.getDisplay(this).setCurrent(mainForm);
new Thread(this).start();

}

public void pauseApp(){}
public void destroyApp(boolean unconditional){}

public void run(){

      final UUID uuid = new UUID("102030405060708090A0B0C0D0E0F010", false);

      mainForm.setTitle("Servidor");

            try{
                  LocalDevice local = LocalDevice.getLocalDevice();
                  System.out.println("Endereco BT:"+local.getBluetoothAddress());
                  System.out.println("Nome:"+local.getFriendlyName());
                  if (!local.setDiscoverable(DiscoveryAgent.GIAC)){
                        mainForm.append("Falha ao mudar para modo Discoverable");
                        return;
                  }
            StreamConnectionNotifier notifier = (StreamConnectionNotifier)
            Connector.open("btspp://localhost:" + uuid.toString() +";name=TesteRudi");

            StreamConnection conn = notifier.acceptAndOpen();

            InputStream in = conn.openInputStream();
            ByteArrayOutputStream out = new ByteArrayOutputStream();

            int data;
            while ((data=in.read()) != -1) {
                  out.write(data);
            }

            mainForm.append(out.toString());
            in.close();
            conn.close();
            notifier.close();

            }catch (BluetoothStateException e){
                  mainForm.append("BluetoothStateException:"+e.getMessage());
            }catch (IOException e){
                  mainForm.append("IOException:"+e.getMessage());
            }

}
public void commandAction (Command c, Displayable d){
if (c == exitCommand){
destroyApp(true);
notifyDestroyed();
}
}
}

by: idurPosted on 2004-05-07 at 18:33:03ID: 11019629

by: jimmackPosted on 2004-05-10 at 01:43:43ID: 11029473

What is the full output from the server (ie. the complete text of the exception)?

Are you sure that the bluetooth device can be used in this way from the emulator? The bluetooth extensions are primarily designed for accessing the bluetooth facilities within a handset. It is possible that the emulator developers have included access to the bluetooth device on the P.C., but it's not something I've dealt with myself.

by: idurPosted on 2004-05-10 at 05:31:30ID: 11030497

Done, I got it... thanks

by: jimmackPosted on 2004-05-10 at 06:01:34ID: 11030679

:-)

by: Woody_FXPosted on 2004-05-19 at 05:34:22ID: 11107263

Hey,

If you want a working example of Bluetooth check out Ben Hui website.

www.benhui.com

Loads of nice links and articles.

Also a good forum to discuss bluetooth (do a search in the J2ME forum)

is www.forum.nokia.com

Take it easy ;-)

20120131-EE-VQP-002

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Question

Bluetooth J2ME - Need practical help with connection example

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j2me

bluetooth

example

Wireless Technologies

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