Trying to understand and get Nx_TCP_Echo_Client to work on B-L462E-CELL1

[JFlowers]

OK, I have a STM32L462RE Discovery Kit (apparently a.k.a. B-L462E-CELL1).

I am trying to get its sole Demonstration application to work (STM32CubeExpansion_CELLULAR_V7.1.0\Projects\B-L462E-CELL1\Demonstrations\Nx_TCP_Echo_Client), but I can’t even tell how it is supposed to work.

 

I see “TCP_Echo_Client” in its name, so I assume if I have a simple TCP echo server running on my workstation that if I do the appropriate port forwarding through my router along with the appropriate Windows Firewall settings, then I should see the B-L462E-CELL1 connect to my local TCP Echo Server.

 

Is that correct?

Further, I assume that in this file:

STM32CubeExpansion_CELLULAR_V7.1.0\Projects\B-L462E-CELL1\Demonstrations\Nx_TCP_Echo_Client\NetXDuo\App\tcp_echo_client.c

I should change TCP_SERVER_PORT from 7 to whatever TCP port my local TCP Echo server is running on, AND I should change the TCP_SERVER_ADDRESS IP_ADDRESS(52,215,34,155) in that same file from 52,215,34,155 (which implies 52.215.34.155) to whatever my public facing router’s WAN address is.

 

Is that correct?

If all of that is right and my SIM card is working right, which I think it is - I’m see messages like this on bootup: “Network is up with IP 10.228.182.49” on TeraTerm - then I should see “10.228.182.49” (or whatever IP address is given my B-L462E-CELL1 on bootup) connect to my local TCP echo server.

Is that correct?

Further, I assume that on my TeraTerm console connected to the B-L462E-CELL1, that I will see some sort of confirmation that my local TCP Echo server replied back to the B-L462E-CELL1 with the exact same message that the B-L462E-CELL1 originally sent to it (to my local TCP echo server).

Is that correct?

Where do I change the message that the B-L462E-CELL1 sends to my local TCP echo server?

Help, please.

 

[STackPointer64]

Hello @JFlowers,

It seems you were able to run the TCP Echo part by commenting out the SNTP time request, which is a great step forward. However, SNTP relies on UDP, and it is highly likely that your SIM provider is blocking UDP traffic or the SNTP service in particular.

Additionally, the IP address on your cellular board (10.x.x.x) is private, which means it requires Network Address Translation (NAT) to access the internet. UDP packets often encounter challenges with NAT. Routers may temporarily cache local-to-outside UDP port mappings, but this cache doesn’t persist for long, so there’s no guarantee that UDP packets will consistently get through.

To address these issues, you may consider contacting your SIM provider to obtain a public IP address, which can help bypass NAT-related issues. 

Best regards,