MQTT Connection Error -12

[jmerri95]

Hello, 

I am working on connecting a NRF9161 to a MQTT server (EMQX) but i am getting a connection error (-12), I was hoping someone could help me navigate this one. It looks like the error is connected to memory for the CA cert. 

Some context:

I have successfully connected to the Nordic MQTT development server (8883 and 1883) by following the steps in the the MQTT over LTE example. When I try to connect to the EMQX server over port 8883 I get this error. 

Below are some details about the config files. 

I've tried maxing out the NRF_MODEM_LIB_HEAP to 4096 but that did not resolve the error. 4096 is the internal limit. 

[00:00:23.223,907] <inf> Simkura_SB6_READER: New buffer
[00:00:23.271,453] <inf> Simkura_SB6_READER: TX buffer sent
[00:00:25.633,087] <err> Simkura_SB6_MAIN: Error in mqtt_connect: -12
[00:00:25.641,082] <inf> Simkura_SB6_MAIN: Reconnecting in 60 seconds...
[00:00:30.129,333] <inf> Simkura_SB6_NETWORK: RRC mode: Idle
[00:01:26.237,762] <inf> Simkura_SB6_NETWORK: RRC mode: Connected

# Memory

CONFIG_HEAP_MEM_POOL_SIZE=16384

CONFIG_MAIN_STACK_SIZE=8192

CONFIG_NRF_MODEM_LIB_HEAP_SIZE=4096

Is there anyway to override the heap limit for the modem? 

Thank you, 

Jack

[Håkon Alseth]

Hi,

 

Are you setting up a secure connection towards the server on port 8883, and use the .crt file as linked here?

https://www.emqx.com/en/mqtt/public-mqtt5-broker

 

Here's a more in-depth guide on how to add TLS to your MQTT connection:

https://academy.nordicsemi.com/courses/cellular-iot-fundamentals/lessons/lesson-4-cellular-fundamentals/topic/lesson-4-exercise-2/

 

Kind regards,

Håkon

[jmerri95]

Hello, 

I apologize, I didn't describe this issue very well. I found another ticket that is right on point (Case ID: 275308). 

I followed these steps and am still getting a -12 error code. 

[Håkon Alseth]

Hi,

 

Did you follow the lesson 4, exercise 2?

If you take the solution (see here https://github.com/NordicDeveloperAcademy/cell-fund/tree/master/v2.8.x-v2.7.0/l4/l4_e2_sol), then download the emqx certificate, convert it as per the lesson, it should create a header in src/certificate.h.

Then you need to change prj.conf::CONFIG_MQTT_BROKER_HOSTNAME="broker.emqx.io"

 

I followed these two steps and it ran as expected on my end:

*** Booting nRF Connect SDK v2.8.0-a2386bfc8401 ***
*** Using Zephyr OS v3.7.99-0bc3393fb112 ***
[00:00:00.295,776] <inf> Lesson4_Exercise2: Initializing modem library
[00:00:00.587,615] <inf> Lesson4_Exercise2: Comparing credentials: Match
[00:00:00.587,646] <inf> Lesson4_Exercise2: Connecting to LTE network
[00:00:04.252,380] <inf> Lesson4_Exercise2: RRC mode: Connected
[00:00:05.233,703] <inf> Lesson4_Exercise2: Network registration status: Connected - home network
[00:00:05.233,764] <inf> Lesson4_Exercise2: Connected to LTE network
[00:00:05.467,071] <inf> Lesson4_Exercise2: IPv4 Address found 34.243.217.54
[00:00:05.467,834] <inf> Lesson4_Exercise2: TLS enabled
[00:00:06.937,255] <inf> Lesson4_Exercise2: MQTT client connected
[00:00:06.937,316] <inf> Lesson4_Exercise2: Subscribing to: devacademy/subscribe/topic len 26
[00:00:07.113,281] <inf> Lesson4_Exercise2: SUBACK packet id: 1234
[00:00:13.869,964] <inf> Lesson4_Exercise2: RRC mode: Idle
[00:00:29.376,647] <inf> Lesson4_Exercise2: Publishing: Hi from nRF91 Series device
[00:00:29.376,678] <inf> Lesson4_Exercise2: to topic: devacademy/publish/topic len: 24
[00:00:29.481,536] <inf> Lesson4_Exercise2: RRC mode: Connected
[00:00:29.724,182] <inf> Lesson4_Exercise2: PUBACK packet id: 60412

 

Kind regards,

Håkon

[jmerri95]

Hi Hakon, 

Sorry to leave you hanging here. I decided to pivot and use the MQTT server in the NRF cloud. It has been working great so far. 

The multi cloud example had a couple pre-built features that I've been using as well. 

[Håkon Alseth]

Hi,

 

It is great to hear that you got things working! Hope you have a wonderful day!

 

Kind regards,

Håkon