RE: How to determine if NTN connected?

P_J — Mon, 24 Nov 2025 07:49:30 GMT

Thanks for the reply Achim.

This makes sense, I will change my code to monitor for the lost registration after sending and "RRC active" as you suggested.

RE: How to determine if NTN connected?

Achim Kraus — Sun, 23 Nov 2025 19:41:27 GMT

> What's the recommended approach for verifying NTN connection status before transmission?

Just to be clear, this approach already spends a lot of energy, I'm not sure, why this is considered to be preferred instead of just sending the UDP message.

> Since we're using UDP, send() always succeeds regardless of actual connection status.

That's not my experience. It succeeds, when sending from sleep-mode. But if the modem isn't sleeping and not registered in the network it will fail.

> Without proper verification before transmission, we risk sending data into a black hole when the modem isn't actually registered to the satellite
network.

If you send the UDP message in "sleeping mode", the mode considers to be registered, therefore the success (otherwise it would be required to block, maybe for several seconds). The message wakes up the modem, and the modem tries to switch to RRC active and transmits the message. In the (rare) case this fails, the modem will report the lost registration (+CEREG). Therefore wait for "RRC active" and then a few seconds to check, if the modem reports the lost registration. If it stay registered, the message is sent.