LTEM MQTT messages lost

Hello everyone, I got an issue using tge SARA R412M module to post MQTT message to a broker. As I cannot afford to lose a single message, I set the qos to 1.

Most of the time everything is working just fine buf a few messages get lost now and then.

Every single command:


gets a

+UMQTTC: 2,1

response, so in theory everything is ok on my side but the broker never shows the message.

So, I have two questions:

-does a “+UMQTTC: 2,1” implies that the broker got the message? Or merely that it left the modem?
-after sending the message I almost immediately disconnect the device (“AT+UMQTTC=0”), is it good practice? As there is a transaction going on between the modem and the broker because of qos 1, I am wondering if I should leave the modem on for a while and, if so, for how long?

Thanks a lot for any help.


Hi @fabry-dev,

We also encounter issues with the buildin MQTT of the R4 modules.
We use for MQTT our custom library.

Let us know if you also get a more stable connection with these libraries.

Best regards,