code: @Override
    public PollResult startPoll(PollController conn)
    {
      if (! _lifecycle.isActive()) {
        log.warning(this + " select disabled");
          
        return PollResult.CLOSED;
      }
      else if (_selectMax <= _connectionCount.get()) {
        log.warning(this + " keepalive overflow "
                    + _connectionCount + " max=" + _selectMax);
        System.out.println("OVERFLOW:");
        
        return PollResult.CLOSED;
      }
      
      if (! conn.toKeepaliveStart()) {
        return PollResult.CLOSED;
      }
  
      return poll(conn);
    }
docs: Adds a keepalive connection.
  
  @param conn the connection to register as keepalive
  
  @return true if the connection changes to the keepalive state