code: public void start() {
          stop(); // <-- If server is not running nothing happens.
  
          if (!isInitialized()) {
              onInit();
              server = __buildServer();
          }
  
          try {
              server.start();
          } catch (Exception e) {
              throw new RuntimeException(e);
          }
      }
docs: Starts server.
  
  If server is running, it will be restarted.