nRF91 as UDP server

RE: nRF91 as UDP server

Achim Kraus — Fri, 28 Mar 2025 11:50:04 GMT

As I explained, there is usually a NAT between the cellular ip-network and the public ip-network.

Pretty similar to a DSL-internet-router. There it's also easy to use clients, but if you want to run an server in your home network, then you need "port forwarding" (for cellular that's not the way).

You will need either "always traffic" (energy + data volume) or something as a VPN or ip-tunel or whatever spans then a private ip-network between your device and server.

RE: nRF91 as UDP server

rrna — Fri, 28 Mar 2025 11:20:08 GMT

Thanks for your reply. I forgot to mention that my issue is I receive no data on the nrf91 devkit.

Coap+DTLS where the nrf91 is the client works perfectly fine. I need a web application to be able to initiate some action on the devkit, so I was trying to setup a UDP server on the devkit - here I receive no data

RE: nRF91 as UDP server

Achim Kraus — Thu, 27 Mar 2025 19:09:46 GMT

[quote userid="140459" url="~/f/nordic-q-a/120253/nrf91-as-udp-server"]Any ideas what the issue could be?[/quote]

You didn't mention the issue.

Using cellular IP is commonly using something as an "IP breakout", where the cellular IP-traffic is feed into the public IP.

That comes usually with a NAT (Network Address Translation). It works, if the device initiates the traffic, that allocates an mapping in the NAT and from that on your server may send something back. If no messages are exchanged, the NAT will remove the mapping after an timeout. See my article NAT .

Therefore you have two options:

Permanently exchange messages, e.g. every 30s

Use a "private network", that may come as VPN or IPsec. In some cases it comes with extra costs at your provider.

By the way, if you don't want to keep the device in IDLE (energy consumption), you will need eDRX.