anchor.diff:    }
   
     /// Open the connection with serial port.
  -  Future<bool> open() {
  +  Future open() {
       if(_ttyFd != -1){
         throw new StateError("$portname is yet open.");
       }
  
positive.code:   int get fd => _ttyFd;
  
    /// Close the connection.
    Future<bool> close(){
      _checkOpen();
      final completer = new Completer<bool>();
      final replyPort = new ReceivePort();
  
negative.code: 
    /// Read data send from the serial port
    Stream<List<int>> get onRead {
      StreamController<int> controller = new StreamController();
      _onReadControllers.add(controller);
      return controller.stream;
    }
  