Thank you for looking into this. To give a little bit more background:
I have a temp sensor from a third party (Efento) that has its own operating system. It uses UDP to send a hexadecimal message to a server. I have a working setup with LTE-M sensors and my own server that accepts incoming UDP traffic.
I am now trying out the new (different) NB-IoT sensors with the cards from IoT creators. As the cards cannot reach public IP’s, I am trying to use the server to forward the CoAP payload to an HTTP endpoint. This is working via 172.27.131.100:15683.
Now, I look for a way to make the server acknowledge the message. I am not sure how to do this. The only thing I can think of, is sending a downlink message, but I suspect that receiving a (new) downlink message is not the same as receiving an acknowledgment, to the sensor.
Am I correct that the server is not acknowledging the message?