code: function OpenEventObserver(clientPort, serverPort) {
      events.EventEmitter.call(this);
  
      this.isClientPortOpen = false;
      this.isServerPortOpen = false;
  
      clientPort.on('open', this._clientPortOpenHandler(this));
      serverPort.on('open', this._serverPortOpenHandler(this));
  }
docs: Local Helper Object to wait for the open event on two Serial Port objects