code: @Override
      public void afterConnectionEstablished(final WebSocketSession webSocketSession) {
          logger.debug("[afterConnectionEstablished] id = {}", webSocketSession.getId());
          this.session = webSocketSession;
  
          synchronized (notifyConnectionObject) {
              notifyConnectionObject.notifyAll();
          }
      }
docs: Is called after a websocket session was established.
  @param webSocketSession websocket session that was established