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  1. Qt
  2. QTBUG-44792

QBluetoothSocket tries to connect to RFCOMM channel -1



    • Type: Bug
    • Status: Closed
    • Priority: P2: Important
    • Resolution: Done
    • Affects Version/s: 5.3.2
    • Fix Version/s: 5.4.2
    • Labels:
    • Platform/s:


      There is a flaw in the solution of QTBUG-40172: in Android versions below 4.2, the getServiceChannel call doesn't always return BluetoothDevice.ERROR in case of an error. It can also return -1. QBluetoothSocket only checks for BluetoothDevice.ERROR, so the result is that QBluetoothSocket tries to use channel -1 to connect, but this is an invalid channel.

      More background info:
      Up to Android 4.1 the getServiceChannel function calls a lower level function on the BluetoothService and return ERROR in case an exception is thrown.

      /** @hide */
      public int getServiceChannel(ParcelUuid uuid) {
           try {
               return sService.getRemoteServiceChannel(mAddress, uuid);
           } catch (RemoteException e) {Log.e(TAG, "", e);}
           return BluetoothDevice.ERROR;

      That lower level function however does not seem to throw any exception itself, but does return -1 in case of an error.

      public int getRemoteServiceChannel(String address, ParcelUuid uuid) {
          mContext.enforceCallingOrSelfPermission(BLUETOOTH_PERM, "Need BLUETOOTH permission");
          if (!isEnabledInternal()) return -1;
          if (!BluetoothAdapter.checkBluetoothAddress(address)) {
              return BluetoothDevice.ERROR;
          // Check if we are recovering from a crash.
          if (mDeviceProperties.isEmpty()) {
              if (mDeviceProperties.updateCache(address) == null)
                  return -1;
          Map<ParcelUuid, Integer> value = mDeviceServiceChannelCache.get(address);
          if (value != null && value.containsKey(uuid))
              return value.get(uuid);
          return -1;

      Starting from Android 4.2, this function always returns ERROR.

      /** @hide */
      public int getServiceChannel(ParcelUuid uuid) {
           try {
               return sService.getRemoteServiceChannel(this, uuid);
           } catch (RemoteException e) {Log.e(TAG, "", e);}*/
           return BluetoothDevice.ERROR;


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            • Assignee:
              ablasche Alex Blasche
              mbuijs Martijn Buijs
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              • Created:

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