transmit method
Implementation
void transmit(Uint8List txBuf) {
final _txBuf = malloc.allocate<ffi.Uint8>(txBuf.length);
var index = 0;
for (var value in txBuf) {
_txBuf[index++] = value;
}
_native.transmit(_fd, _txBuf, txBuf.length);
malloc.free(_txBuf);
}