public async Task <SubscribeResult> Subscribe(MqttSubscribePacket subscribePacket)
{
if (subscribePacket == null)
{
throw new ArgumentNullException(nameof(subscribePacket));
}
var retainedApplicationMessages = await _retainedMessagesManager.GetMessagesAsync().ConfigureAwait(false);
var result = new SubscribeResult();
// The topic filters are order by its QoS so that the higher QoS will win over a
// lower one.
foreach (var originalTopicFilter in subscribePacket.TopicFilters.OrderByDescending(f => f.QualityOfServiceLevel))
{
var interceptorContext = await InterceptSubscribe(originalTopicFilter).ConfigureAwait(false);
var finalTopicFilter = interceptorContext?.TopicFilter ?? originalTopicFilter;
var acceptSubscription = interceptorContext?.AcceptSubscription ?? true;
var closeConnection = interceptorContext?.CloseConnection ?? false;
if (string.IsNullOrEmpty(finalTopicFilter.Topic) || !acceptSubscription)
{
result.ReturnCodes.Add(MqttSubscribeReturnCode.Failure);
result.ReasonCodes.Add(MqttSubscribeReasonCode.UnspecifiedError);
}
else
{
result.ReturnCodes.Add(ConvertToSubscribeReturnCode(finalTopicFilter.QualityOfServiceLevel));
result.ReasonCodes.Add(ConvertToSubscribeReasonCode(finalTopicFilter.QualityOfServiceLevel));
}
if (closeConnection)
{
result.CloseConnection = true;
}
if (!acceptSubscription || string.IsNullOrEmpty(finalTopicFilter.Topic))
{
continue;
}
var subscription = CreateSubscription(finalTopicFilter, subscribePacket);
await _eventDispatcher.SafeNotifyClientSubscribedTopicAsync(_clientSession.ClientId, finalTopicFilter).ConfigureAwait(false);
FilterRetainedApplicationMessages(retainedApplicationMessages, subscription, result);
}
return(result);
}
static void FilterRetainedApplicationMessages(IList <MqttApplicationMessage> retainedApplicationMessages, Subscription subscription, SubscribeResult subscribeResult)
{
for (var i = retainedApplicationMessages.Count - 1; i >= 0; i--)
{
var retainedApplicationMessage = retainedApplicationMessages[i];
if (retainedApplicationMessage == null)
{
continue;
}
if (subscription.RetainHandling == MqttRetainHandling.DoNotSendOnSubscribe)
{
// This is a MQTT V5+ feature.
continue;
}
if (subscription.RetainHandling == MqttRetainHandling.SendAtSubscribeIfNewSubscriptionOnly && !subscription.IsNewSubscription)
{
// This is a MQTT V5+ feature.
continue;
}
if (!MqttTopicFilterComparer.IsMatch(retainedApplicationMessage.Topic, subscription.Topic))
{
continue;
}
var queuedApplicationMessage = new MqttQueuedApplicationMessage
{
ApplicationMessage = retainedApplicationMessage,
IsRetainedMessage = true,
SubscriptionQualityOfServiceLevel = subscription.QualityOfServiceLevel
};
if (subscription.Identifier > 0)
{
queuedApplicationMessage.SubscriptionIdentifiers = new List <uint> {
subscription.Identifier
};
}
subscribeResult.RetainedApplicationMessages.Add(queuedApplicationMessage);
retainedApplicationMessages[i] = null;
}
}