@Override
    public void setFlowControl(FlowControl flowcontrol) throws IOException {
        if (flowcontrol != FlowControl.NONE)
            throw new UnsupportedOperationException();
    }
use simple USB request supported by all devices to test if connection is still valid
usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CommonUsbSerialPort.java