Kent Andersen Kent Andersen - 1 year ago 114
Android Question

android bluetooth can't connect

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();

public void onCreate(final Bundle savedInstanceState) {


mDevicesList = new ArrayList<BluetoothDevice>();

// Register the BroadcastReceiver
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter);


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 {
mDialog = new BluetoothDeviceDialog(this, mDevicesList);, "");


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());

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

protected void onDestroy() {

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();

mDialog = new BluetoothDeviceDialog(this, mDevicesList);, "");

super.onActivityResult(requestCode, resultCode, data);

public void onEvent(EventMessage.DeviceSelected event) {


BluetoothDevice device = event.getDevice();

ConnectThread connectThread = new ConnectThread(device);

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() {
// Cancel discovery because it will slow down the connection

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");
Log.d("kent", "Connected!");
} catch (IOException connectException) {
// Unable to connect; close the socket and get out
try {
Log.d("kent", "failed to connect");

} catch (IOException closeException) { }

Log.d("kent", "Connected!");

/** Will cancel an in-progress connection, and close the socket */
public void cancel() {
try {
} 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"

Answer Source

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

This might help:

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

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