private int sendAcmControlMessage(int request, int value, byte[] buf) throws IOException {
            int len = mConnection.controlTransfer(
                    USB_RT_ACM, request, value, mControlIndex, buf, buf != null ? buf.length : 0, 5000);
            if(len < 0) {
                throw new IOException("controlTransfer failed");
            }
            return len;
        }
USB CDC/ACM serial driver implementation.

@author mike wakerly (opensource@hoho.com)
@see <a
     href="http://www.usb.org/developers/devclass_docs/usbcdc11.pdf">Universal
     Serial Bus Class Definitions for Communication Devices, v1.1</a>
usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CdcAcmSerialDriver.java