docs: public synchronized long sendMessage(AbstractRequestMessage message) {
      log.debug("Sending {} to {}", message, this);
      message.setTicketNumber(this.nextTicketNumber.getAndIncrement());
      this.outstandingRequests.put(Long.valueOf(message.getTicketNumber()),
          message);
      this.session.write(message);
      return message.getTicketNumber();
    }