anchor.diff:        if (result != null) {
           // TODO return value ?
           _ttyFd = -1;
  -        _state = CLOSED;
           completer.complete(true);
         } else {
           completer.completeError("Unexpected error");
  
positive.code: 
    // TODO rename sendString
    // TODO send with List<int>
    // TODO Future
    Future<bool> send(String data){
      // TODO check OPEN
      var completer = new Completer<bool>();
  
negative.code: 
  class SerialPort {
  
  
    static const List<int> AUTHORIZED_BAUDATE_SPEED =  const [50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 4000000];
  
    final String portname;
    final int baudrate;
  
    int _ttyFd = -1;
  
    SerialPort(this.portname, {this.baudrate : 9600}){
      if(!AUTHORIZED_BAUDATE_SPEED.contains(baudrate)){
        throw new ArgumentError("Unknown baudrate speed=$baudrate");
      }
  