Android中的蓝牙连接期间未创建连接（失败或中止）的异常

Question

I am working on a project which makes use of an android tablet(iball 3G 7271) that runs on 4.1.2 and is made of MTK processor AND an RN42 bluetooth (chip on a PCB).These two modules communicate with each other to transfer data among them via bluetooth.

I am facing issues.wherein at certain instances I repeatedly get exceptions stating 'Connection is not created (failed or aborted)'.I have found the instances as described below:

I copied the relevant code from the BlueTerm app(from playstore) and made a sample app to test BT connectivity.Blueterm is an app to test bluetooth connectivity between a device and RN42.

1) I Connected/disconnected the app to RN42,and found that it was working all the time.Proper connection and disconnection was happening. 2) I Simulated power failure(by switching off just the RN42 module),I then disconnected & reconnected the BT connection between app and RN42 & found that the tablet was getting re-connected with RN42 without much issue.

3)

Before re-installation, the app was disconnected from RN42 ; result- after re-installation BT reconnection to RN42 in the re installed app works fine.

Before re-installation the app was in connected state to RN42;result- after re-installation BT reconnection to RN42 doesnt happen. I traced that the exception that comes for Test case 2 is :

W/System.err(4603): java.io.IOException: [JSR82] connect: Connection is not created (failed or aborted).
W/System.err(4603):     at android.bluetooth.BluetoothSocket.connect(BluetoothSocket.java:395)

This was the exception I was getting again and again few days back.So now I kinda know when this exception can get thrown.

NOTE: For 'Test case2' ,here even un-installing and re-installing the app and then trying to connect app to RN42 doesnt work.We need to reboot the tablet to make the app connect to BT again.Moreover,I even tried connecting the real BlueTerm app(in test case 2),but it also did not get connected.So then I tried switching OFF and ON the tablet's BT.I observed that by switching off and then switching ON the BT and then trying to establish BT connection between tablet and RN42 was happening .But now, I was not getting any input signals from RN42 to tablet,but was able to just send data from tablet to RN42.

For the above Test case2,on these devices the app does get connected to BT after re-installation,even if it was/was not connected to RN42 via BT prior to re-installation.

Below is the code of my app and the log cat exception:

BlueTerm.java

        @SuppressLint("HandlerLeak")
        public class BlueTerm extends Activity {

            BluetoothSocket Socket;
            OutputStream DataOut;
            InputStream DataIn;


            // Intent request codes
            private static final int REQUEST_CONNECT_DEVICE = 1;
            private static final int REQUEST_ENABLE_BT = 2;

            private static TextView mTitle;

            // Name of the connected device
            private String mConnectedDeviceName = null;

            /**
             * Set to true to add debugging code and logging.
             */
            public static final boolean DEBUG = true;

            /**
             * Set to true to log each character received from the remote process to the
             * android log, which makes it easier to debug some kinds of problems with
             * emulating escape sequences and control codes.
             */
            public static final boolean LOG_CHARACTERS_FLAG = DEBUG && false;

            /**
             * Set to true to log unknown escape sequences.
             */
            public static final boolean LOG_UNKNOWN_ESCAPE_SEQUENCES = DEBUG && false;

            /**
             * The tag we use when logging, so that our messages can be distinguished
             * from other messages in the log. Public because it's used by several
             * classes.
             */
            public static final String LOG_TAG = "BlueTerm";

            // Message types sent from the BluetoothReadService Handler
            public static final int MESSAGE_STATE_CHANGE = 1;
            public static final int MESSAGE_READ = 2;
            public static final int MESSAGE_WRITE = 3;
            public static final int MESSAGE_DEVICE_NAME = 4;
            public static final int MESSAGE_TOAST = 5;  

            // Key names received from the BluetoothChatService Handler
            public static final String DEVICE_NAME = "device_name";
            public static final String TOAST = "toast";

            private BluetoothAdapter mBluetoothAdapter = null;

            private static BluetoothSerialService mSerialService = null;

            /** Called when the activity is first created. */
            @Override
            public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);

                if (DEBUG)
                    Log.e(LOG_TAG, "+++ ON CREATE +++");
                setContentView(R.layout.main);


                mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

                mSerialService = new BluetoothSerialService(this, mHandlerBT);

                Button buzzerOn = (Button) findViewById(R.id.button1);
                buzzerOn.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        Log.v("BlueTerm","Buzzer button clicked");

                        //send("37".getBytes());
                        send(bigIntToByteArray(37));
                    }
                });

                Button buzzerOff = (Button) findViewById(R.id.button2);
                buzzerOff.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        Log.v("BlueTerm","Buzzer button clicked");

                        //send("37".getBytes());
                        send(bigIntToByteArray(30));
                    }
                });

                Button recon = (Button) findViewById(R.id.button3);
                recon.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        Log.v("BlueTerm","recon button clicked");

                        BluetoothAdapter iballAdapter = BluetoothAdapter.getDefaultAdapter();
                        BluetoothDevice RN42_Device = iballAdapter.getRemoteDevice("00:06:66:49:57:5F");

                        try {
                            Socket = RN42_Device.createRfcommSocketToServiceRecord(UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"));
                            DataOut = Socket.getOutputStream();
                            DataIn = Socket.getInputStream();

                        } catch (Exception e1) {
                            e1.printStackTrace();
                        }
                        if (DataIn != null) {
                            Log.d("AppFunctions","DataIn is not null,so making it NULL");
                            try {DataIn.close();} catch (Exception e) {}
                            DataIn = null;
                        }

                        Log.i("AppFunctions", "DataOut -" + DataOut);
                        if (DataOut != null) {
                            Log.d("AppFunctions","DataOut is not null,so making it NULL");
                            try {DataOut.close();} catch (Exception e) {}
                            DataOut = null;
                        }

                        Log.i("AppFunctions", "Socket -" + Socket);
                        if (Socket != null) {
                            Log.d("AppFunctions","Socket is not null,so making it NULL");
                            try {Socket.close();} catch (Exception e) {}
                            Socket = null;
                        }

                        try {
                            Socket = RN42_Device.createRfcommSocketToServiceRecord(UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"));
                            Socket.connect();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        if (mSerialService != null)
                            mSerialService.stop();
                            mSerialService.start();

                    }
                });

                if (DEBUG)
                    Log.e(LOG_TAG, "+++ DONE IN ON CREATE +++");
            }

            @Override
            public void onStart() {
                super.onStart();
                if (DEBUG)
                    Log.e(LOG_TAG, "++ ON START ++");

                mEnablingBT = false;
            }

            @Override
            public synchronized void onResume() {
                super.onResume();

                if (DEBUG) {
                    Log.e(LOG_TAG, "+ ON RESUME +");
                }       
                    if (mSerialService != null) {
                        Log.v("BlueTerm","mSerialService is NOT null");
                        // Only if the state is STATE_NONE, do we know that we haven't started already
                        if (mSerialService.getState() == BluetoothSerialService.STATE_NONE) {
                            // Start the Bluetooth chat services
                            Log.v("BlueTerm","starting BT chat service");
                            mSerialService.start();
                        }
                    }
                }
            }

            @Override
            public synchronized void onPause() {
                super.onPause();
                if (DEBUG)
                    Log.e(LOG_TAG, "- ON PAUSE -");
            }

            @Override
            public void onStop() {
                super.onStop();
                if(DEBUG)
                    Log.e(LOG_TAG, "-- ON STOP --");
            }


            @Override
            public void onDestroy() {
                super.onDestroy();
                if (DEBUG)
                    Log.e(LOG_TAG, "--- ON DESTROY ---");

                if (mSerialService != null)
                    mSerialService.stop();

            }

            public int getConnectionState() {
                return mSerialService.getState();
            }


            public void send(byte[] out) {
                mSerialService.write( out );
            }

            // The Handler that gets information back from the BluetoothService
            private final Handler mHandlerBT = new Handler() {

                @Override
                public void handleMessage(Message msg) {            
                    switch (msg.what) {
                    case MESSAGE_STATE_CHANGE:
                        if(DEBUG) Log.i(LOG_TAG, "MESSAGE_STATE_CHANGE: " + msg.arg1);
                        switch (msg.arg1) {
                        case BluetoothSerialService.STATE_CONNECTED:
                            break;

                        case BluetoothSerialService.STATE_CONNECTING:
                            break;

                        case BluetoothSerialService.STATE_LISTEN:
                        case BluetoothSerialService.STATE_NONE:
                            Log.d("BlueTerm","inside STATE_NONE in handler");
                            break;
                        }
                        break;
                    case MESSAGE_WRITE:
                        if (mLocalEcho) {
                            byte[] writeBuf = (byte[]) msg.obj;
                        }

                        break;

                    case MESSAGE_READ:
                        byte[] readBuf = (byte[]) msg.obj;              
                        Log.d("incoming writebytes",""+readBuf.toString());

                        break;

                    case MESSAGE_DEVICE_NAME:
                        // save the connected device's name
                        mConnectedDeviceName = msg.getData().getString(DEVICE_NAME);
                        Toast.makeText(getApplicationContext(), "Connected to "
                                       + mConnectedDeviceName, Toast.LENGTH_SHORT).show();
                        break;
                    case MESSAGE_TOAST:
                        Toast.makeText(getApplicationContext(), msg.getData().getString(TOAST),
                                       Toast.LENGTH_SHORT).show();
                        break;
                    }
                }
            };    

            public void onActivityResult(int requestCode, int resultCode, Intent data) {
                if(DEBUG) Log.d(LOG_TAG, "onActivityResult " + resultCode);
                switch (requestCode) {

                case REQUEST_CONNECT_DEVICE:

                    // When DeviceListActivity returns with a device to connect
                    if (resultCode == Activity.RESULT_OK) {
                        // Get the device MAC address
                        String address = "00:06:66:49:57:5F";
                        // Get the BLuetoothDevice object
                        BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
                        // Attempt to connect to the device
                        mSerialService.connect(device);                
                    }
                    break;

                case REQUEST_ENABLE_BT:
                    // When the request to enable Bluetooth returns
                    if (resultCode == Activity.RESULT_OK) {
                        Log.d(LOG_TAG, "BT not enabled");

                    }
                }
            }

            @Override
            public boolean onCreateOptionsMenu(Menu menu) {
                MenuInflater inflater = getMenuInflater();
                inflater.inflate(R.menu.option_menu, menu);
                mMenuItemConnect = menu.getItem(0);
                return true;
            }

            @Override
            public boolean onOptionsItemSelected(MenuItem item) {
                switch (item.getItemId()) {
                case R.id.connect:

                    if (getConnectionState() == BluetoothSerialService.STATE_NONE) {                
                        String address = "00:06:66:49:57:5F";
                        // Get the BLuetoothDevice object
                        BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
                        Log.d("BlueTerm","device: " + device);
                        // Attempt to connect to the device
                        mSerialService.connect(device);
                    }
                    else
                        if (getConnectionState() == BluetoothSerialService.STATE_CONNECTED) {
                            mSerialService.stop();
                            mSerialService.start();
                        }
                    return true;
                case R.id.preferences:
                    //doPreferences();
                    return true;
                case R.id.menu_special_keys:
                    //doDocumentKeys();
                    return true;
                }
                return false;
            }

            private byte[] bigIntToByteArray( final int i ) {
                BigInteger bigInt = BigInteger.valueOf(i);      
                return bigInt.toByteArray();
            }
        }

---

BluetoothService:

        /**
         * This class does all the work for setting up and managing Bluetooth
         * connections with other devices. It has a thread that listens for
         * incoming connections, a thread for connecting with a device, and a
         * thread for performing data transmissions when connected.
         */
        public class BluetoothSerialService {
            // Debugging
            private static final String TAG = "BluetoothReadService";
            private static final boolean D = true;


            private static final UUID SerialPortServiceClass_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

            // Member fields
            private final BluetoothAdapter mAdapter;
            private final Handler mHandler;
            private ConnectThread mConnectThread;
            private ConnectedThread mConnectedThread;
            private int mState;


            // Constants that indicate the current connection state
            public static final int STATE_NONE = 0;       // we're doing nothing
            public static final int STATE_LISTEN = 1;     // now listening for incoming connections
            public static final int STATE_CONNECTING = 2; // now initiating an outgoing connection
            public static final int STATE_CONNECTED = 3;  // now connected to a remote device

            /**
             * Constructor. Prepares a new BluetoothChat session.
             * @param context  The UI Activity Context
             * @param handler  A Handler to send messages back to the UI Activity
             */
            public BluetoothSerialService(Context context, Handler handler) {
                mAdapter = BluetoothAdapter.getDefaultAdapter();
                mState = STATE_NONE;
                mHandler = handler;
               // mEmulatorView = emulatorView;
            }

            /**
             * Set the current state of the chat connection
             * @param state  An integer defining the current connection state
             */
            private synchronized void setState(int state) {
                if (D) Log.d(TAG, "setState() " + mState + " -> " + state);
                mState = state;
                Log.d("BluetoothSerialService","state : " + state);
                // Give the new state to the Handler so the UI Activity can update
                mHandler.obtainMessage(BlueTerm.MESSAGE_STATE_CHANGE, state, -1).sendToTarget();
            }

            /**
             * Return the current connection state. */
            public synchronized int getState() {
                return mState;
            }

            /**
             * Start the chat service. Specifically start AcceptThread to begin a
             * session in listening (server) mode. Called by the Activity onResume() */
            public synchronized void start() {
                if (D) Log.d(TAG, "start");

                // Cancel any thread attempting to make a connection
                if (mConnectThread != null) {
                    mConnectThread.cancel(); 
                    mConnectThread = null;
                }

                // Cancel any thread currently running a connection
                if (mConnectedThread != null) {
                    mConnectedThread.cancel(); 
                    mConnectedThread = null;
                }

                setState(STATE_NONE);
            }

            /**
             * Start the ConnectThread to initiate a connection to a remote device.
             * @param device  The BluetoothDevice to connect
             */
            public synchronized void connect(BluetoothDevice device) {
                if (D) Log.d(TAG, "connect to: " + device);

                // Cancel any thread attempting to make a connection
                if (mState == STATE_CONNECTING) {
                    if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
                }

                // Cancel any thread currently running a connection
                if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}

                // Start the thread to connect with the given device
                mConnectThread = new ConnectThread(device);
                mConnectThread.start();
                setState(STATE_CONNECTING);
            }

            /**
             * Start the ConnectedThread to begin managing a Bluetooth connection
             * @param socket  The BluetoothSocket on which the connection was made
             * @param device  The BluetoothDevice that has been connected
             */
            public synchronized void connected(BluetoothSocket socket, BluetoothDevice device) {
                if (D) Log.d(TAG, "connected");

                // Cancel the thread that completed the connection
                if (mConnectThread != null) {
                    mConnectThread.cancel(); 
                    mConnectThread = null;
                }

                // Cancel any thread currently running a connection
                if (mConnectedThread != null) {
                    mConnectedThread.cancel(); 
                    mConnectedThread = null;
                }

                // Start the thread to manage the connection and perform transmissions
                mConnectedThread = new ConnectedThread(socket);
                mConnectedThread.start();

                // Send the name of the connected device back to the UI Activity
                Message msg = mHandler.obtainMessage(BlueTerm.MESSAGE_DEVICE_NAME);
                Bundle bundle = new Bundle();
                bundle.putString(BlueTerm.DEVICE_NAME, device.getName());
                msg.setData(bundle);
                mHandler.sendMessage(msg);

                setState(STATE_CONNECTED);
            }

            /**
             * Stop all threads
             */
            public synchronized void stop() {
                if (D) Log.d(TAG, "stop");


                if (mConnectThread != null) {
                    mConnectThread.cancel(); 
                    mConnectThread = null;
                }

                if (mConnectedThread != null) {
                    mConnectedThread.cancel(); 
                    mConnectedThread = null;
                }

                setState(STATE_NONE);
            }

            /**
             * Write to the ConnectedThread in an unsynchronized manner
             * @param out The bytes to write
             * @see ConnectedThread#write(byte[])
             */
            public void write(byte[] out) {
                Log.e("BluetoothSerialService","Inside write fn" + "    :" + out.toString());
                // Create temporary object
                ConnectedThread r;
                // Synchronize a copy of the ConnectedThread
                synchronized (this) {
                    if (mState != STATE_CONNECTED) return;
                    r = mConnectedThread;
                }
                // Perform the write unsynchronized
                r.write(out);
            }

            /**
             * Indicate that the connection attempt failed and notify the UI Activity.
             */
            private void connectionFailed() {
                setState(STATE_NONE);

                // Send a failure message back to the Activity
                Message msg = mHandler.obtainMessage(BlueTerm.MESSAGE_TOAST);
                Bundle bundle = new Bundle();
                bundle.putString(BlueTerm.TOAST, "Unable to connect device");
                msg.setData(bundle);
                mHandler.sendMessage(msg);
            }

            /**
             * Indicate that the connection was lost and notify the UI Activity.
             */
            private void connectionLost() {
                setState(STATE_NONE);

                // Send a failure message back to the Activity
                Message msg = mHandler.obtainMessage(BlueTerm.MESSAGE_TOAST);
                Bundle bundle = new Bundle();
                bundle.putString(BlueTerm.TOAST, "Device connection was lost");
                msg.setData(bundle);
                mHandler.sendMessage(msg);
            }

            /**
             * This thread runs while attempting to make an outgoing connection
             * with a device. It runs straight through; the connection either
             * succeeds or fails.
             */
            private class ConnectThread extends Thread {
                private final BluetoothSocket mmSocket;
                private final BluetoothDevice mmDevice;

                public ConnectThread(BluetoothDevice device) {
                    mmDevice = device;
                    BluetoothSocket tmp = null;

                    // Get a BluetoothSocket for a connection with the
                    // given BluetoothDevice
                    try {
                        tmp = device.createRfcommSocketToServiceRecord(SerialPortServiceClass_UUID);
                    } catch (IOException e) {
                        Log.e(TAG, "create() failed", e);
                    }
                    mmSocket = tmp;
                }

                public void run() {
                    Log.e(TAG, "BEGIN mConnectThread");
                    setName("ConnectThread");

                    // Always cancel discovery because it will slow down a connection
                    mAdapter.cancelDiscovery();

                    // Make a connection to the BluetoothSocket
                    try {
                        // This is a blocking call and will only return on a
                        // successful connection or an exception
                        mmSocket.connect();
                    } catch (IOException e) {
                        connectionFailed();
                        // Close the socket
                        try {
                            mmSocket.close();
                        } catch (IOException e2) {
                            Log.e(TAG, "unable to close() socket during connection failure", e2);
                        }
                        // Start the service over to restart listening mode
                        //BluetoothSerialService.this.start();
                        return;
                    }

                    // Reset the ConnectThread because we're done
                    synchronized (BluetoothSerialService.this) {
                        mConnectThread = null;
                    }

                    // Start the connected thread
                    connected(mmSocket, mmDevice);
                }

                public void cancel() {
                    try {
                        mmSocket.close();
                    } catch (IOException e) {
                        Log.e(TAG, "close() of connect socket failed", e);
                    }
                }
            }

            /**
             * This thread runs during a connection with a remote device.
             * It handles all incoming and outgoing transmissions.
             */
            private class ConnectedThread extends Thread {
                private final BluetoothSocket mmSocket;
                private final InputStream mmInStream;
                private final OutputStream mmOutStream;


                public ConnectedThread(BluetoothSocket socket) {
                    Log.e(TAG, "create ConnectedThread");
                    mmSocket = socket;
                    InputStream tmpIn = null;
                    OutputStream tmpOut = null;

                    // Get the BluetoothSocket input and output streams
                    try {
                        tmpIn = socket.getInputStream();
                        tmpOut = socket.getOutputStream();
                    } catch (IOException e) {
                        Log.e(TAG, "temp sockets not created", e); 
                    } 

                    mmInStream = tmpIn;
                    mmOutStream = tmpOut;
                }

                public void run() {
                    Log.e(TAG, "BEGIN mConnectedThread");
                    byte[] buffer = new byte[1024];
                    int bytes;

                    // Keep listening to the InputStream while connected
                    Log.e(TAG, "Entering while");
                    while (true) {
                        Log.e(TAG, "Inside while");
                        try {
                            // Read from the InputStream
                            bytes = 0;
                            Log.d("incoming bytes",""+bytes);
                            Log.e("BT","Inputstream :" + mmInStream);
                            //bytes = mmInStream.read(buffer);
                            bytes = mmInStream.read();
                            Log.d("incoming bytes",""+bytes);
                            //mEmulatorView.write(buffer, bytes);
                            // Send the obtained bytes to the UI Activity
                            mHandler.obtainMessage(BlueTerm.MESSAGE_READ, bytes, -1, buffer).sendToTarget();

                            String a = buffer.toString();  
                            a = ""; 
                        } catch (Exception e) {
                            Log.e(TAG, "disconnected", e); 
                            connectionLost();  
                            break;
                        }
                        bytes = 0;
                    }
                    //Log.e(TAG, "Outside while");
                }

                /**
                 * Write to the connected OutStream.
                 * @param buffer  The bytes to write
                 */
                public void write(byte[] buffer) {
                    try {
                        Log.d("writing to outStream byte :", buffer.toString());
                        mmOutStream.write(buffer);

                        // Share the sent message back to the UI Activity
                        //mHandler.obtainMessage(BlueTerm.MESSAGE_WRITE, buffer.length, -1, buffer).sendToTarget();
                    } catch (IOException e) {
                        Log.e(TAG, "Exception during write", e);
                    }
                }

                public void cancel() {
                    try {
                        mmSocket.close();
                    } catch (Exception e) {
                        Log.e(TAG, "close() of connect socket failed", e);
                    }
                }
            }
        }

---

Logcat error:

W/System.err(4603): java.io.IOException: [JSR82] connect: Connection is not created (failed or aborted). W/System.err(4603): at android.bluetooth.BluetoothSocket.connect(BluetoothSocket.java:395)

---

I suspect that this error could be thrown because the app is not able to get access to the active BT port,in the above mentioned test case.Reason is because I read this site : https://code.google.com/p/android/issues/detail?id=5427 (See answer #19 by dknop) I observe that none of this issue occur on samsung s2/grand/nexus devices which I tested on.My error could also be due to MTK processors/its BT firmware/iball custom android issue.( http://redacacia.me/2012/07/17/overcoming-android-bluetooth-blues-with-reflection-method/ )

Has anyone faced a similar problem? Any help would be appreciated.Many thanks !

Answer 1

I've tested Bluetooth connectivity on dozens of different tablets, and I've seen some VERY flaky behavior. My apps always call createRfcommSocketToServiceRecord(...) in a loop because sometimes it will fail for no apparent reason, only to succeed on a later attempt. And the API doesn't let you distinguish between transient and permanent failures. Some tablets give you a clue in the text of the error message, but others don't.

I typically try to connect 100 times at 100ms intervals, and then stop and ask the user if the device they're trying to connect to is turned on and in range. On one particular tablet model I've tested, it's not unusual for the connection to fail more than 300 times... and then it will suddenly work like nothing was ever wrong.

Answer 2

I have used this piece of code to make my connectivity to Bluetooth device(ie Bluetooth printer) stable. Now it connect 9.9 times out of 10. If still some error occurred i reset my Bluetooth programmatically again call this piece of code then it connect 10 times out of 10.

public boolean connectToPrinter(String printerName) throws IOException 
    {
        BluetoothAdapter.getDefaultAdapter().cancelDiscovery();

        BluetoothDevice device = getPrinterByName(printerName);

        if (bluetoothSocket != null) 
        {
            bluetoothSocket.close();
        }


        try {

            Method m=device.getClass().getMethod("createRfcommSocket", new Class[]{int.class});
            bluetoothSocket=    (BluetoothSocket) m.invoke(device, 1);          

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


        if (bluetoothSocket == null)
            return false;

        bluetoothSocket.connect();

        return true;
    }

here is the code of getPrinterByName():

private BluetoothDevice getPrinterByName(String printerName) 
    {
        Set<BluetoothDevice> pairedDevices = BluetoothAdapter.getDefaultAdapter().getBondedDevices();

        for (BluetoothDevice device : pairedDevices) 
        {

            Log.e("","device name: "+device.getName());

            if (device.getName() == null)
                continue;
            if (device.getName().contains(printerName)) 
            {
                remoteDevice = device;
                //              pairPrinter(printerName);
                return remoteDevice;
            }
        }
        return null;
    }

bluetoothSocket is the Object of BluetoothSocket class. and don't forget to run this code in thread otherwise this will block your Main Thread. :-)

Answer 3

hi friend just replace the code to connect to bluetoothsocket by the code using reflection to establish connection.....

private BluetoothSocket createBluetoothSocket(BluetoothDevice device) throws IOException {
      if(Build.VERSION.SDK_INT >= 10){
          try {
              final Method  m = device.getClass().getMethod("createInsecureRfcommSocketToServiceRecord", new Class[] { UUID.class });
              return (BluetoothSocket) m.invoke(device, MY_UUID);
          } catch (Exception e) {
              Log.e(TAG, "Could not create Insecure RFComm Connection",e);
          }
      }
      return  device.createRfcommSocketToServiceRecord(MY_UUID);
  }

Answer 4

Quote: I observed that by switching off and then switching ON the BT and then trying to establish BT connection between tablet and RN42 was happening .But now, I was not getting any input signals from RN42 to tablet,but was able to just send data from tablet to RN42.

So, before reinstalling app it WAS possible to receive input signals from rn42?