docs: public int addPoller(PollItem pollItem, IZLoopHandler handler, Object arg)
      {
          if (pollItem.getRawSocket() == null && pollItem.getSocket() == null) {
              return -1;
          }
  
          SPoller poller = new SPoller(pollItem, handler, arg);
          pollers.add(poller);
  
          dirty = true;
          if (verbose) {
              System.out.printf(
                                "I: zloop: register %s poller (%s, %s)\n",
                                pollItem.getSocket() != null ? pollItem.getSocket().getType() : "RAW",
                                        pollItem.getSocket(),
                                        pollItem.getRawSocket());
          }
          return 0;
      }