public class ChatActivity extends BaseChatActivity {

    private final AtomicBoolean keepThreadAlive = new AtomicBoolean(true);
    private final List<String> sendBuffer = new ArrayList<>();

    @Override
    public void sendString(final String string) {
        sendBuffer.add(string);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        new Thread(new CommunicationRunnable()).start();
    }

    private class CommunicationRunnable implements Runnable {

        @Override
        public void run() {
            final UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);

            final UsbDevice device=getIntent().getParcelableExtra(ConnectActivity.DEVICE_EXTRA_KEY);

            UsbEndpoint endpointIn = null;
            UsbEndpoint endpointOut = null;

            final UsbInterface usbInterface = device.getInterface(0);

            for (int i = 0; i < device.getInterface(0).getEndpointCount(); i++) {

                final UsbEndpoint endpoint = device.getInterface(0).getEndpoint(i);
                if (endpoint.getDirection() == UsbConstants.USB_DIR_IN) {
                    endpointIn = endpoint;
                }
                if (endpoint.getDirection() == UsbConstants.USB_DIR_OUT) {
                    endpointOut = endpoint;
                }

            }

            if (endpointIn == null) {
                printLineToUI("Input Endpoint not found");
                return;
            }

            if (endpointOut == null) {
                printLineToUI("Output Endpoint not found");
                return;
            }

            final UsbDeviceConnection connection = usbManager.openDevice(device);

            if (connection == null) {
                printLineToUI("Could not open device");
                return;
            }

            final boolean claimResult = connection.claimInterface(usbInterface, true);

            if (!claimResult) {
                printLineToUI("Could not claim device");
            } else {
                final byte buff[] = new byte[Constants.BUFFER_SIZE_IN_BYTES];
                printLineToUI("Claimed interface - ready to communicate");

                while (keepThreadAlive.get()) {
                    final int bytesTransferred = connection.bulkTransfer(endpointIn, buff, buff.length, Constants.USB_TIMEOUT_IN_MS);
                    if (bytesTransferred > 0) {
                        printLineToUI("host> "+new String(buff, 0, bytesTransferred));
                    }

                    synchronized (sendBuffer) {
                        if (sendBuffer.size()>0) {
                            final byte[] sendBuff=sendBuffer.get(0).toString().getBytes();
                            connection.bulkTransfer(endpointOut, sendBuff, sendBuff.length, Constants.USB_TIMEOUT_IN_MS);
                            sendBuffer.remove(0);
                        }
                    }
                }
            }

            connection.releaseInterface(usbInterface);
            connection.close();
        }
    }

    @Override
    protected void onStop() {
        super.onStop();
        keepThreadAlive.set(false);
    }
}