modbs and GPRS

Hi there, its been a while :slight_smile:

I need some general guidance. I have a GSM808 shield on my UNO and would like to use a Modbus protocol to send/receive data between the remote GPRS/UNO and my localhost. I can connect to a TCP server using NGROK and using sockettest I can establish 2 way comms no problem. I use SCADABR and have set up a tunnel to my localhost and I can poll the TCP socket I set up with NGROK.

Now the challenge. I have been using various Arduino Modbus libraries with Ethernet and Wifi with great success, but how do I set up Modbus to send receive data packets using GPRS? The GSM AT command AT+CIPSEND opens the remote comms, but has to be terminated with ctrl-Z. How do I allow packets to be sent and received using CIPSEND? Is there no way I can allow the CIPSEND command to terminate with ctrl-Z every time a packet is sent/received? My gut tells me this is blindingly simple, yet I am not a programmer.

I would really appreciate anyone commenting on some general guidelines/ideas on how to do this.

Yes sure, I can go out and buy a Netbiter for R15 000 (1000 USD), but I am protyping a remote machine and compared to the cost of my setup (~100 USD), its a no brainer...

Thanks and regards,
Jan