Android Bluetooth SPP Server

Question

I'm new in Android programming and i now have a problem. I want to use my android phone as a bluetooth server, which means that when I open a special Activity the phone should listen to other Bluetooth devices (which are already paired) and the other device can open a conncection to my android phone. So it should be like the phone is a pheripheral device, like a bt speaker. So the pairing is still done. And in found out that I have to use the SPP mode. When it's connect i want to send an receive simple byte streams. I found a app called 'bluetooth spp tools pro' ( https://play.google.com/store/apps/details?id=mobi.dzs.android.BLE_SPP_PRO&hl=de ) which does almost everything i want. But here the problem is that the phones works as client and opens the connection.

So maybe you could help me and give me some tips to understand what i have to do.

Thanks for the help:)

EDIT: Now I tried a Example from Android and It seems like it is almost working. I can connect my pc with the Smartphone and the smartphone connects with it. But when it has connected, the app crashes and I don't know why... maybe you can tell me why ma app crashes.. here the code:

public class BluetoothServer extends AppCompatActivity {

public BluetoothAdapter mBluetoothAdapter;
private static final UUID MY_UUID_SECURE = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

private AcceptThread mSecureAcceptThread;

private TextView textViewStatus;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_bluetooth_server);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    textViewStatus = (TextView) findViewById(R.id.BluetoothServerTextView);
}

@Override
protected void onDestroy() {
    super.onDestroy();
    mSecureAcceptThread.cancel();
    mSecureAcceptThread  = null;
}

public void onClickOpenBluetoothServer(View view) {

    // Setup Bluetooth Adapter
    mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

    //Enable Discoverbility
    Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
    discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);
    startActivity(discoverableIntent);
    textViewStatus.append("\nDiscoverable Added!");

    //Starting Accepting Thread
    mSecureAcceptThread = new AcceptThread();
    mSecureAcceptThread.start();
}


/**
 * Accepting Thread mit run();
 */
private class AcceptThread extends Thread {
    private final BluetoothServerSocket mmServerSocket;

    public AcceptThread() {
        BluetoothServerSocket tmp = null;
        try {
            // MY_UUID is the app's UUID string, also used by the client code
            tmp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord("PAKSAFE", MY_UUID_SECURE);
        } catch (IOException e) { }
        mmServerSocket = tmp;
        textViewStatus.append("\nAcceptThread Created!");
    }

    public void run() {
        BluetoothSocket socket = null;
        // Keep listening until exception occurs or a socket is returned
        while (true) {
            try {
                textViewStatus.append("\nListening");
                socket = mmServerSocket.accept();
            } catch (IOException e) {
                break;
            }
            // If a connection was accepted
            if (socket != null) {
                // Do work to manage the connection (in a separate thread)
                //manageConnectedSocket(socket);
                textViewStatus.setText("Acccepted");
                try {
                    mmServerSocket.close();
                } catch (IOException e) {
                    break;
                }
                break;
            }
        }
    }

    /** Will cancel the listening socket, and cause the thread to finish */
    public void cancel() {
        try {
            mmServerSocket.close();
        } catch (IOException e) { }
    }
}

}

Answer 1

Create a RFCOMM socket (which is also known as the Serial Port Profile (SPP)) and listen for incoming data.

Android has an API for that purposes, use BluetoothServerSocket and listen to incoming data.

An example of BluetoothServerSocket usage can be found here