MQTT - Keep-alive mechanism - Receive callback

[dslc]

I don't think that the client->poll_time should be reset in the mqtt_recv_cb(): https://github.com/MaJerle/gsm-at-lib/blob/develop/gsm_at_lib/src/apps/mqtt/gsm_mqtt_client.c#L848 .

The Mosquitto server I am testing with was closing the connection until I commented this line out.

Scenario:

• The device using your GSM AT library connects successfully to MQTT broker - and subscribes to topic of interest
• Keep-alive interval set to 30 seconds
• Device does not publish on any topic
• Another remote client connects to broker and publishes on topic of interest - so (in mqtt_recv_cb) device resets the keep-alive timer (client->poll_time)
• The time between PINGREQ messages is then too long - so the server closes the connection

[MaJerle]

Fixed on develop branch. Thanks

[dslc]

@MaJerle Thank you!