anchor.diff:  
     Future<bool> close(){
       _checkOpen();
  -    var completer = new Completer<bool>();
  -    var replyPort = new ReceivePort();
  +    final completer = new Completer<bool>();
  +    final replyPort = new ReceivePort();
       _servicePort.send([replyPort.sendPort, _CLOSE_METHOD, _ttyFd]);
       replyPort.first.then((List result) {
         if (result[0] == null) {
  
positive.code: 
    Future<bool> _writeOneByte(int byte){
      _checkOpen();
      var completer = new Completer<bool>();
      var replyPort = new ReceivePort();
      _servicePort.send([replyPort.sendPort, _WRITE_BYTE_METHOD, _ttyFd, byte]);
      replyPort.first.then((result) {
        if (result[0] == null) {
  
negative.code:   // TODO rename sendString ?
    Future<bool> writeString(String data){
      _checkOpen();
      final completer = new Completer<bool>();
      final replyPort = new ReceivePort();
      _servicePort.send([replyPort.sendPort, _WRITE_METHOD, _ttyFd, data]);
      replyPort.first.then((result) {
        if (result[0] == null) {
  