MQTT-SN subscriptions dropped out

[martinezcp]

Environment

• OS: Raspbian 4.19.97
• Erlang/OTP: 22/10.6
• EMQ: 4.02

Description

I have some devices connected through MQTT-SN which require to keep the subscriptions after they are disconnected from the gateway. I am pretty sure I have something not configured but I cannot find it.

I am trying with command line clients in order to see if everything is working or not. It works fine with the MQTT but it is not with MQTT-SN.

This works and keep subsription after disconnecting the client (Client receives messages after reconnecting)

mosquitto_sub -h 127.0.0.1 -p 11883 -q 1 -t "topic/test" -i "test_mqtt" -c

This works and client receives messages while it is connected but broker does not keep the subscription after disconnected. Neither it receives messages after reconnecting.

./mqtt-sn-sub -h 127.0.0.1 -p 5224 -q 1 -t "topic/test" -i "test_sn" -c

I think I need to update something in order to keep subscriptions for the SN part.

If I connect both clients, disconnect them and publish a message with:

mosquitto_pub -h 127.0.0.1 -p 11883 -q 1 -t "topic/test" -m "hello"

After reconnecting both clients, the mqtt is the only one receiving the message.

Whenever I connect a SN client, the log shows the following:

2020-02-28 09:59:51.492 [error] <<"test_sn">> MQTT-SN(127.0.0.1:35358): StateName: idle, Unexpected Event: {cast,
                                                          {event,
                                                           connected}}
2020-02-28 09:59:51.499 [error] <<"test_sn">> MQTT-SN(127.0.0.1:35358): StateName: connected, Unexpected Event: {cast,
                                                               {event,
                                                                updated}}

[HJianBo]

Hi, @martinezcp It is a bug to handle the Clean Session mechanism. We are very sorry to bring trouble to you.

We plan to fix it at next next version (may 4.1.beta.1 or 4.0.5

Thanks for your report here :)

[HJianBo]

Hi, @martinezcp We have fixed it in v4.0.5