'Asynchronously initiate connection to ZK.
:returns: An event object that can be checked to see if the
connection is alive.
:rtype: :class:`~threading.Event` compatible object.'

def start_async(self):

    if self._live.is_set():
        return self._live
    self._safe_close()
    self._stopped.clear()
    self._writer_stopped.clear()
    self.handler.start()
    self._connection.start()
    return self._live
