I'm trying to send data from a Digi Xbee 3 LTE-M/NB-IoT module via HTTP POST/GET requests to a third party cloud based server (https://thingsboard.cloud). The server uses SSL, and I have configured my module accordingly, using XCTU:
"IP" to "TCPSSL".
"TL" to "TLSv1.2"
"DE" to "1BB" for TCP port 443
And I've downloaded the associated public certificate (single pem file) and loaded it on the flash.
I basically did everything in this thread : "https://www.digi.com/support/forum/68818/https-example-with-xbee3-cellular-cat-1?show=68818#q68818". Unlike its author, I'm able to send GET/POST requests to www.google.com both via transparent and API mode and receive answers from the server. (via IP 188.8.131.52 for API mode).
However, I can't get any answer from most servers, among which en.wikipedia.org or thingsboard.cloud which is my main goal. I suspect that this is somehow linked to the IP address of the server (for example, I use 184.108.40.206 for thingsboard but it leads to a self-certified website. I can't ping it either...). When I send a 0x23 frame in API mode, all I get in return is a "85: Unknown error" delivery status...
Basic TCP requests on port 80 such as the numbersapi example in the user manual work fine, which is why I think the problem is related to SSL.
If someone has already managed to make this module communicate with HTTPS servers, I would gladly take any advice they can share.