ESP32-S3 + SIM7672G: SSL connection takes too long using SSLClient library (over 1 minute)

Hello,

I’m working on a project using an ESP32-S3 connected to an LTE modem (SIM7672G). I’m using the SSLClient library to establish an SSL connection for MQTT communication.

However, I’m facing an issue:

The SSL connection takes about 1 minute to establish when using the SIM7672G modem.

Interestingly, when I switch to another modem, the SIMCOM A7672G, using the exact same code and setup, the SSL connection is established almost instantly.

Details:

  • Both modems (SIM7672G and A7672G) are similar in specs.
  • I’m not using AT commands for SSL or MQTT — the ESP32 handles the SSL stack directly via the SSLClient library.
  • I did test AT commands for SSL and MQTT as a workaround, and while it works, it’s not suitable for my project as I require MQTT to run through the ESP32 stack, not the modem.
  • The network signal and SIM card are the same in both cases.

My Questions:

  1. Why might the SIM7672G be significantly slower in establishing an SSL connection compared to the A7672G?
  2. Is there something specific in the SIM7672G that could affect TCP/SSL performance?
  3. Is there any known compatibility issue between SIM7672G and the SSLClient library or ESP32-S3?

I’d appreciate any insights or suggestions on debugging or optimizing this setup.
If needed, I can also share code snippets.

Thanks!

Are both these modem’s running the latest firmware?

SIM7672: SIM7672X Series

SIM7672 platform are based off Qualcomm’s 216 LTE IoT modem..

A7672G: A7672G

A7672G is based off ASR Micro: ASR1603

Regards,

2 Likes

Yes both running on same firmware.

This is weird because I saw same issue on SIM7670G too.

While I have A7672G, and SIM7000G modem too and both are running fine with same firmware.

As i am doing SSL through ESP32, it is not making sense to me.

Thanks,
Rushik

Sorry one more question, since i have SSL capabilities on LTE itself. Is there any way to do SSL configuration with AT command and other connections like mqtts and https are done on esp32?

Have you looked at this project in your research? GitHub - vshymanskyy/TinyGSM: A small Arduino library for GSM modules, that just works

Looking thru their git log, they do have native SSL Support for these models..

Regards,

Hi,

Yes I have used TinyGsm and tried to use, A7672 implementation in this library. But it doesn’t work.