MQTT Timeout in nRF9160

[uhrm]

Hi,

We have been using the MQTT sample code with a few iBasis SIM cards for some time without issue. This week we made a test where the mqtt_disconnect function in the sample code was called to force a disconnection; the problem is that after this the boards will always fail to connect due MQTT timeout. We swapped the SIM cards to ones not used in the test and the boards now work fine again and can connect without issues.

Since the issue appears to follow the SIM cards used in the test, does anyone know how/if this behavior could be related to the test of calling mqtt_disconnect? Can the SIM cards somehow be diagnosed?

Note that the failing SIM cards have enough data left, so this should not be the issue as reported in this other thread https://devzone.nordicsemi.com/f/nordic-q-a/52986/mqtt-connect-timeout.

Thank you

[Didrik Rokhaug]

Hi,

Do you have any log files?

If you can capture a modem trace, that would also be helpful.

During your tests, do you also disconnect from the cellular network?

Does it happen after only one disconnect?

Do you do any additional cleanup, or are you re-using the same mqtt_client struct?

If you put one of the "failed" SIM cards in a new device, would that device work?

Best regards,

Didrik

[uhrm]

Hi Didrik,

It was indeed a data issue. The problem seems that the SIM data information in nRF cloud takes a while to refresh (at least a day?). So, when the issue happened and we checked in nRF cloud the same day, the SIMs apparently still had data available, but checking one or two days later they were completely out. Once we realized this we just purchased more and the SIMs worked right away.

Thanks

uhrm