@afzal_m Thanks! It’s working now:)
I didn’t upgrade the firmware. That step seemed a bit complicated when I started. I wasn’t succesful at reading the current firmware to begin with. In the meanwhile, I had contact with the vendor, who told me the module is running the latest firmware (packaging was sealed).
Earlier, I had already tried the AT+CGDCONT command with and without quotes (all kinds of), all resulting in ERROR. Then I noticed that changing the 0 into an 1 returns OK, with and without quotes. I don’t know if that’s significant. The result of at+cereg? was still +CEREG:0,5.
But creating the socket without quotes returned OK now and the remaining steps were easy now. I was able to deliver the Hello World message.
To be clear, I never had a positive result from AT+CGDCONT=0,IP,cdp.iot.t-mobile.nl. at+cereg? still returns +CEREG:0,5. Is that okay?
Thanks again for your time.