android bluetooth can't connect

Question

I've been having this problem for a while and haven't been able to figure it out.

I have a android application that puts all paired devices in a listview. When you click one of the list items, it will initiate a request to connect to that bluetooth device.

I can get the list of devices with their addresses no problem. The problem is that once I try to connect I get an IOException on socket.connect();

The error message is as follows: "connect read failed, socket might closed or timeout, read ret: -1"

Here is my code. ANY suggestions would be appreciated. I'm pretty stuck on this.

fyi: the "onEvent" methods is a library that simplifies callbacks...that part works. When the user clicks on a list items this method is called "public void onEvent(EventMessage.DeviceSelected event)"

public class EcoDashActivity extends BaseActivity {
public static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
private BluetoothAdapter mBluetoothAdapter;
private int REQUEST_ENABLE_BT = 100;
private ArrayList<BluetoothDevice> mDevicesList;
private BluetoothDeviceDialog mDialog;
private ProgressDialog progressBar;
private int progressBarStatus = 0;
private Handler progressBarHandler = new Handler();
@Override
public void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.main);
    mDevicesList = new ArrayList<BluetoothDevice>();
    // Register the BroadcastReceiver
    IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
    registerReceiver(mReceiver, filter);
    setupBluetooth();
}
private void setupBluetooth() {
    mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    if (mBluetoothAdapter == null) {
        // Device does not support Bluetooth
        Toast.makeText(this, "Device does not support Bluetooth", Toast.LENGTH_SHORT).show();
    }
    if (!mBluetoothAdapter.isEnabled()) {
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
    } else {
        searchForPairedDevices();
        mDialog = new BluetoothDeviceDialog(this, mDevicesList);
        mDialog.show(getFragmentManager(), "");
    }
}
private void searchForPairedDevices() {
    Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
    // If there are paired devices
    if (pairedDevices.size() > 0) {
        // Loop through paired devices
        for (BluetoothDevice device : pairedDevices) {
            // Add the name and address to an array adapter to show in a ListView
            mDevices.add(device.getName() + "\n" + device.getAddress());
            mDevicesList.add(device);
        }
    }
}
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        // When discovery finds a device
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // Get the BluetoothDevice object from the Intent
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // Add the name and address to an array adapter to show in a ListView
            mDevicesList.add(device);
        }
    }
};
@Override
protected void onDestroy() {
    super.onDestroy();
    unregisterReceiver(mReceiver);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REQUEST_ENABLE_BT) {
        if (resultCode == RESULT_OK) {
            Toast.makeText(this, "BT turned on!", Toast.LENGTH_SHORT).show();
            searchForPairedDevices();
            mDialog = new BluetoothDeviceDialog(this, mDevicesList);
            mDialog.show(getFragmentManager(), "");
        }
    }
    super.onActivityResult(requestCode, resultCode, data);
}
public void onEvent(EventMessage.DeviceSelected event) {
    mDialog.dismiss();
    BluetoothDevice device = event.getDevice();
    ConnectThread connectThread = new ConnectThread(device);
    connectThread.start();
}
public class ConnectThread extends Thread {
    private final BluetoothSocket mmSocket;
    private final BluetoothDevice mmDevice;
    public ConnectThread(BluetoothDevice device) {
        // Use a temporary object that is later assigned to mmSocket,
        // because mmSocket is final
        BluetoothSocket tmp = null;
        mmDevice = device;
        // Get a BluetoothSocket to connect with the given BluetoothDevice
        try {
            // MY_UUID is the app's UUID string, also used by the server code
            tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
        } catch (IOException e) { }
        mmSocket = tmp;
    }
    public void run() {
        setName("ConnectThread");
        // Cancel discovery because it will slow down the connection
        mBluetoothAdapter.cancelDiscovery();
        try {
            // Connect the device through the socket. This will block
            // until it succeeds or throws an exception
            Log.d("kent", "trying to connect to device");
            mmSocket.connect();
            Log.d("kent", "Connected!");
        } catch (IOException connectException) {
            // Unable to connect; close the socket and get out
            try {
                Log.d("kent", "failed to connect");
                mmSocket.close();
            } catch (IOException closeException) { }
            return;
        }
        Log.d("kent", "Connected!");
    }
    /** Will cancel an in-progress connection, and close the socket */
    public void cancel() {
        try {
            mmSocket.close();
        } catch (IOException e) { }
    }
}

Here is my logcat. Pretty short.

07-22 10:37:05.129: DEBUG/kent(17512): trying to connect to device
07-22 10:37:05.129: WARN/BluetoothAdapter(17512): getBluetoothService() called with no BluetoothManagerCallback
07-22 10:37:05.129: DEBUG/BluetoothSocket(17512): connect(), SocketState: INIT, mPfd: {ParcelFileDescriptor: FileDescriptor[98]}
07-22 10:37:40.757: DEBUG/dalvikvm(17512): GC_CONCURRENT freed 6157K, 9% free 62793K/68972K, paused 7ms+7ms, total 72ms
07-22 10:38:06.975: DEBUG/kent(17512): failed to connect
07-22 10:38:06.975: DEBUG/kent(17512): read failed, socket might closed or timeout, read ret: -1

That last line is in the "Catch" section of a try/catch...I'm just logging the error message.

Please note, there is about a 20 second gap between "trying to connect to device" and "failed to connect"

Solution 1

The jelly bean bluetooth stack is markedly different from the other versions.

This might help: http://wiresareobsolete.com/wordpress/2010/11/android-bluetooth-rfcomm/

In gist: The UUID is a value that must point to a published service on your embedded device, it is not just randomly generated. The RFCOMM SPP connection you want to access has a specific UUID that it publishes to identify that service, and when you create a socket it must match the same UUID.

If you are targeting 4.0.3 device and above , use fetchUuidsWithSdp() and getUuids() to find all the published services and their associated UUID values. For backward compatibility read the article

Solution 2

I got the same error message after connecting the socket a second time. I simply checked if the socket is already connected.

if(!mmSocket.isConnected())
            mmSocket.connect();

I was testing on Android 4.4.2 (Moto G).

Comments

[Kent Andersen]

GetUUIDs() returns a list of ids. How do you know which one should be used?

[Kent Andersen]

I just tried every UUID that it returned and had the same problem.

[Kent Andersen]

Do you know of a complete code example that i can copy/paste into a new app to just test it out?

[Vrashabh Irde]

I see two bugs reported related to your issue on Android, see if there is any help or workaround here: code.google.com/p/android/issues/detail?id=41415 and code.google.com/p/android/issues/detail?id=41110

[Kent Andersen]

I just tried this on the "Note 2" device, and the code worked great. Bluetooth connected right away. Guess its just a bug with Android 4.2.2 or maybe the nexus 4. I've awarded you the bounty points :) Thanks.

[Kent Andersen]

I feel its worth noting to anyone reading this that my code is connecting to a Bluetooth adapter connected to my car. I'm using it for OBD2 readings. I could not get the app to connect with one adapter, but then I recently purchased another and the code worked perfectly. So, either the problem lies with the adapter, or Android has a bug that doesn't allow to communicate with certain devices.