code: int sendMessageToTopicForSessions(Collection<Session> sessions, MessageToClient mtc, Object payload) {
  		int sended = 0;
  		JsTopicMessageController msgControl = messageControllerManager.getJsTopicMessageController(mtc.getId());
  		Collection<Session> sessionsClosed = new ArrayList<>();
  		for (Session session : sessions) {
  			try {
  				sended += checkAndSendMtcToSession(session, msgControl, mtc, payload);
  			} catch (SessionException se) {
  				sessionsClosed.add(se.getSession());
  			}
  		}
  		if (logger.isDebugEnabled()) {
  			logger.debug("Send message to '{}' topic {} client(s) : {}", new Object[]{mtc.getId(), sessions.size() - sessionsClosed.size(), mtc});
  		}
  		topicManager.removeSessionsToTopic(sessionsClosed);
  		return sended;
  	}
docs: send message to sessions
  apply msgControl to topic
  @param sessions
  @param mtc
  @param payload
  @return