MQTT-SN: How to handle Retransmission of Publish-Messages while Sleeping

[Kolja Vornholt]

Dear all,

MQTT-SN is used on connectionless transport protocols. This is why a retransmission mechanism in case of QoS=1 is necessary in my view. Such a retransmission mechanism can be activated on an MQTT Broker. Now I am wondering what should happen on the MQTT-SN Gateway when MQTT-SN clients are asleep. Does the Gateway should send the Puback to the Broker or should it merge all retransmitted Publish-Messages to one single Message?

I cannot see this question answered in the MQTT-SN Spec.

Do you have a solution?

Thanks a lot and best regards,

Kolja

[Alex Robenko]

If I'm not mistaken, gateway is still connected to the broker while client is asleep. It means from the broker perspective the client is connected and expected to be responsive. As the result, the gateway needs to reply with PUBACK on behalf of the client, while retaining the message(s) internally and then resend them to the client (on behalf of the broker) when the client wakes up. Also when client answers with PUBACK of its own, it should not be forwarded to broker at that stage.

Regards,

Alex

[Seung Yul Baek]

2018년 5월 15일 (화) 오후 5:30, Kolja Vornholt <kolja.v...@gmail.com>님이 작성:

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