Disconnect a bluetooth socket in Android

Question

I'm developing a program in which, from an Android Phone, I have to connect as a client to a Bluetooth medical sensor. I'm using the official Bluetooth API and no problem during connection (SPP profile), but when I end the socket, the sensor is still connected to my phone (although I have close the connection).

Are there any way to make a Bluetooth disconnection? I think there is an intent called ACTION_ACL_CONNECTED, which does that. Can anyone explain me how to use this?

Thanks in advance.

EDITED: Here is the code, if anyone needs additional info, it's a Nonin 4100 medical sensor.

Set<BluetoothDevice> pairedDevices = Activa.myBluetoothAdapter.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
                String name = device.getName();
                if (name.contains("Nonin")) {
                    try {
                        found = true;
//                      socket = device.createRfcommSocketToServiceRecord(UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"));
//                      handler.sendEmptyMessage(5);
//                      Activa.myBluetoothAdapter.cancelDiscovery();
//                      socket.connect();
                        BluetoothDevice hxm = BluetoothAdapter.getDefaultAdapter().getRemoteDevice(device.getAddress());
                        Method m;
                        try {
                            m = hxm.getClass().getMethod("createRfcommSocket", new Class[]{int.class});
                            socket = (BluetoothSocket)m.invoke(hxm, Integer.valueOf(1));
                            handler.sendEmptyMessage(5);
                            socket.connect();
                        } catch (Exception e) {
                            handler.sendEmptyMessage(7);
                            e.printStackTrace();
                            break;
                        }
                        handler.sendEmptyMessage(6);
                        InputStream in = socket.getInputStream();
                        OutputStream out = socket.getOutputStream();
                        byte[] retrieve = { 0x44, 0x31};
                        out.write(retrieve);
                        byte [] ack = new byte [1];
                        in.read(ack);
                        if (ack[0] == 0x15) {
                            cancelMeasurement();
                            return;
                        }
                        byte [] data = new byte [3];
                        long timeStart = System.currentTimeMillis();
                        this.timePassed = System.currentTimeMillis() - timeStart;
                        while ((this.timePassed < (this.time))&&(this.finished)) {
                            try {
                                in.read(data);
                                processData(data);
                                Thread.sleep(1000);
                                this.timePassed = System.currentTimeMillis() - timeStart;
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                        in.close();
                        out.close();
                        socket.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
}

Answer 1

Please remember to close your Input/output streams first, then close the socket.

By closing the streams, you kick off the disconnect process. After you close the socket, the connection should be fully broken down.

If you close the socket before the streams, you may be bypassing certain shutdown steps, such as the (proper) closing of the physical layer connection.

Here's the method I use when its time to breakdown the connection.

/**
 * Reset input and output streams and make sure socket is closed. 
 * This method will be used during shutdown() to ensure that the connection is properly closed during a shutdown.  
 * @return
 */
private void resetConnection() {
        if (mBTInputStream != null) {
                try {mBTInputStream.close();} catch (Exception e) {}
                mBTInputStream = null;
        }

        if (mBTOutputStream != null) {
                try {mBTOutputStream.close();} catch (Exception e) {}
                mBTOutputStream = null;
        }

        if (mBTSocket != null) {
                try {mBTSocket.close();} catch (Exception e) {}
                mBTSocket = null;
        }

}

EDIT: Adding code for connect():

// bluetooth adapter which provides access to bluetooth functionality. 
BluetoothAdapter        mBTAdapter      = null;
// socket represents the open connection.
BluetoothSocket         mBTSocket   = null;
// device represents the peer
BluetoothDevice         mBTDevice       = null; 

// streams
InputStream           mBTInputStream  = null;
OutputStream          mBTOutputStream = null;

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

/**
 * Try to establish a connection with the peer. 
 * This method runs synchronously and blocks for one or more seconds while it does its thing 
 * SO CALL IT FROM A NON-UI THREAD!
 * @return - returns true if the connection has been established and is ready for use. False otherwise. 
 */
private  boolean connect() {

        // Reset all streams and socket.
        resetConnection();

        // make sure peer is defined as a valid device based on their MAC. If not then do it. 
        if (mBTDevice == null) 
                mBTDevice = mBTAdapter.getRemoteDevice(mPeerMAC);

        // Make an RFCOMM binding. 
        try {mBTSocket = mBTDevice.createRfcommSocketToServiceRecord(UUID_RFCOMM_GENERIC);
        } catch (Exception e1) {
                msg ("connect(): Failed to bind to RFCOMM by UUID. msg=" + e1.getMessage());
                return false;
        }

        msg ("connect(): Trying to connect.");

        try {
                mBTSocket.connect();
        } catch (Exception e) {
                msg ("connect(): Exception thrown during connect: " + e.getMessage());
                return false;
        }

        msg ("connect(): CONNECTED!");

        try {
                mBTOutputStream = mBTSocket.getOutputStream();
                mBTInputStream  = mBTSocket.getInputStream();
        } catch (Exception e) {
                msg ("connect(): Error attaching i/o streams to socket. msg=" + e.getMessage());
                return false;
        }

        return true;
}