code: protected synchronized boolean clearPPI (boolean cancel)
      {
          if (_prefPortInterval != null) {
              if (cancel) {
                  _prefPortInterval.cancel();
                  _prefPortInterval.failed();
              }
              _prefPortInterval = null;
              return true;
          }
          return false;
      }
docs: Cancels our preferred port saving interval. This method is called from the communication
  reader thread and the interval thread and must thus be synchronized.