zeroconf.py 文件源码

def check_service(self, info, allow_name_change):
        """Checks the network for a unique service name, modifying the
        ServiceInfo passed in if it is not unique."""

        # This is kind of funky because of the subtype based tests
        # need to make subtypes a first class citizen
        service_name = service_type_name(info.name)
        if not info.type.endswith(service_name):
            raise BadTypeInNameException

        instance_name = info.name[:-len(service_name) - 1]
        next_instance_number = 2

        now = current_time_millis()
        next_time = now
        i = 0
        while i < 3:
            # check for a name conflict
            while self.cache.current_entry_with_name_and_alias(
                    info.type, info.name):
                if not allow_name_change:
                    raise NonUniqueNameException

                # change the name and look for a conflict
                info.name = '%s-%s.%s' % (
                    instance_name, next_instance_number, info.type)
                next_instance_number += 1
                service_type_name(info.name)
                next_time = now
                i = 0

            if now < next_time:
                self.wait(next_time - now)
                now = current_time_millis()
                continue

            out = DNSOutgoing(_FLAGS_QR_QUERY | _FLAGS_AA)
            self.debug = out
            out.add_question(DNSQuestion(info.type, _TYPE_PTR, _CLASS_IN))
            out.add_authorative_answer(DNSPointer(
                info.type, _TYPE_PTR, _CLASS_IN, _DNS_TTL, info.name))
            self.send(out)
            i += 1
            next_time += _CHECK_TIME