How to use the scs.signals.httpd_ready function in scs

def run(self):
        handler = AdminMediaHandler(djwsgi.WSGIHandler())
        sock = listen(self.addrport)
        g = self.spawn(self.server, sock, handler)
        self.info("ready")
        httpd_ready.send(sender=self, addrport=self.addrport,
                         handler=handler, sock=sock)
        return g.wait()

def prepare_signals(self):
        signals.controller_ready.connect(self._component_ready)
        signals.httpd_ready.connect(self._component_ready)
        signals.supervisor_ready.connect(self._component_ready)
        signals.agent_ready.connect(self.on_ready)

ready_event=None, **kwargs):
        self.id = id or gen_unique_id()
        if isinstance(addrport, basestring):
            addr, _, port = addrport.partition(":")
            addrport = (addr, int(port) if port else 8000)
        self.addrport = addrport
        self.connection = celery.broker_connection()
        self.without_httpd = without_httpd
        self.logfile = logfile
        self.loglevel = loglevel
        self.numc = numc
        self.ready_event = ready_event
        self.exit_request = Event()
        if not self.without_httpd:
            self.httpd = gSup(instantiate(self.httpd_cls, addrport),
                              signals.httpd_ready)
        self.supervisor = gSup(instantiate(self.supervisor_cls, sup_interval),
                               signals.supervisor_ready)
        self.controllers = [gSup(instantiate(self.controller_cls,
                                   id="%s.%s" % (self.id, i),
                                   connection=self.connection),
                                 signals.controller_ready)
                                for i in xrange(1, numc + 1)]
        c = [self.supervisor] + self.controllers + [self.httpd]
        c = self.components = list(filter(None, c))
        self._components_ready = dict(zip([z.thread for z in c],
                                          [False] * len(c)))
        super(Agent, self).__init__()