message: Added isOpen function for the listener
diff: @@ -157,6 +157,17 @@ export class Listener {
  });
  }
  + /**
  + * returns a boolean that repressents the open state
  + * @returns a boolean
  + */
  + public isOpen(): boolean {
  + if(this.webSocket){
  + return this.webSocket.readyState === WebSocket.OPEN;
  + }
  + return false;
  + }
  +
  /**
  * Close web socket connection.
  * @returns void
  