Hello.
We have several of our own manufactured boards, containing the nRF9160 cellular modem chip.
We use it for HTTP and HTTPS connectivity, on an application based on the SLM (Serial LTE Modem).
we noticed that opening a socket of port 443 with SSL, fails.
We could overcome this problem, only by burning the https_client example, with a valid certified website, and with certification active.
After running that https_client example and successfully connecting to a socket over SSL, we can run our SLM-based application successfully, and now it too succeeds to open SSL sockets.
This was repeated in 5 out of 5 of our boards, containing the nRF9160 chip.
Using the same SLM-based app, all of them initially failed to connect to a SSL socket.
After running the above-mentioned https-client app on each of the boards, all of these 5 boards are now working, and on all of them the SLM-based application is successfully connecting to SSL sockets.
This process cannot be reversed.
No matter what we do, we cannot make a board now able to connect to an SSL socket, return to its previous state and fail to connect.
This includes erasing the flash, and reprogramming the modem with FW version 1.3.
My colleague opened a similar case, https://devzone.nordicsemi.com/f/nordic-q-a/79055/tls-not-working-without-certificate-provisioning
and I hope this additional info sheds more light on the matter.
What we would like to know is what allows for successful SSL socket connection? What is missing from the SLM app, that exists in the https_client example?
