DevAcademy MQTT example not working

RE: DevAcademy MQTT example not working

fe_lix — Wed, 23 Jul 2025 14:29:48 GMT

I've found an old Hologram SIM card with some data left. With this card the example is working without problems. The fact is that Telekom's prepaid cards do not support LTE-M and NB-IoT.

Thank you very much for your support!

RE: DevAcademy MQTT example not working

fe_lix — Wed, 23 Jul 2025 09:17:48 GMT

Hi,

I called the provider's customer support and asked if my SIM card supports LTE-M / NB-IoT, but they don't even know the protocol. I think this is because private customers are not normally interested in such topics.

I will receive a sim card from Things Mobile in the next few days, so hopefully it should work.
I haven't changed anything in the source code except for the broker address and the topic.
As soon as the new card arrives, I will post an update here.

It's hard to find a provider as a private individual without having a business or working for a company.

RE: DevAcademy MQTT example not working

Felipe Dantas — Tue, 22 Jul 2025 21:11:16 GMT

Please, verify if your sim card really have data credits and if your mobile operator contract have support to NB-IOT/LTE-M access. Otherwise, let´me know if you´ve beem made some change on code of Devacademy example or if you´re using a custom board or a dk.

Sim cards for standard phone plans normally don´t work propertly with LPWA networks like as required for nrf9160.

The most quickly way to verify if you´re connected to internet is just see getaddrinfo() return. If you can´t solve a address like "www.google.com" to "8.8.8.8" it´s means that you don´t have internet connection.

RE: DevAcademy MQTT example not working

fe_lix — Tue, 22 Jul 2025 19:56:17 GMT

Hi,

I've tried it with "mqtt.nordicsemi.academy" and "test.mosquitto.org" and both I can ping and connect to with my MQTT software on the computer. I have the feeling that I can't get an Internet connection even though I have an LTE connection. How can I test this quickly?

When I search the web for “getaddrinfo failed”, I get information about a DNS error. Could this also be the reason?

RE: DevAcademy MQTT example not working

Felipe Dantas — Tue, 22 Jul 2025 18:11:58 GMT

Hi,

Seems that the broker of you´re trying to use is offline. See the return of addrinfo funtion: - 11 = Resource temporarily unavailable (See wiki ERRNO table codes).

My sugest: Try to made a ping test for broker that you´re using and see that it can solve IP of broker address and try use another broker if possible.