SIM7600 HTTPS with TCP/IP AT commands

Projects Networking, Protocols, and Devices
1

I have a sim7600A-H and I'm trying to use the Firebase realtime database REST api to send the device's coordinates

The api requires https, so I originally used the AT+HTTP commands to send data. But that only allows GET/POST/HEAD, I need to send a PUT or PATCH to prevent duplicate data with every request in the database

I created a PUT request using the TCP/IP AT commands and X-HTTP-Method-Override: PUT

However, now I get a 400 Bad Request code and "The plain HTTP request was sent to HTTPS port"

Here's the .ino code I'm using to send the PUT request:

  String tcp_data = "POST /path/to/users/simcom.json? HTTP/1.1\n";
  tcp_data = tcp_data + "Host:project-default-rtdb.firebaseio.com\n";
  tcp_data = tcp_data + "X-HTTP-Method-Override: PUT\n";
  tcp_data = tcp_data + "..."; // Json data here

  sendData("AT+NETCLOSE", 2000, DEBUG);
  sendData("AT+CSOCKSETPN=1", 2000, DEBUG);
  sendData("AT+CIPMODE=0", 2000, DEBUG);
  sendData("AT+NETOPEN", 2000, DEBUG);
  sendData("AT+CIPOPEN=0,\"TCP\",\"project-default-rtdb.firebaseio.com\",443", 2000, DEBUG);
  sendData("AT+CIPSEND=0," + String(tcp_data.length()), 2000, DEBUG);
  sendData(tcp_data, 2000, DEBUG);

Couple of side notes if they are of any use:

I strictly followed this tutorial for AT commands: TCP/IP testing with Simcom SIM7500 and SIM7600 Modules | M2MSupport.net

And followed the documentation for the rest api:
https://firebase.google.com/docs/database/rest/save-data

2

Why don't you just use the PUT method but some non-standard override header? Does you server support that?

3

That works too, just what I last left off with. But even if I do that, it still causes the https error

4

Because you open a standard TCP connection. Your module might support TLS connections but I didn't find a manual of the corresponding AT commands, in the 7600 series manual even the AT commands you use above aren't available. So provide a link to the manual of the commands your module supports!

5

AT+CCHSTART
If you receive OK on UART, then it supports SSL and will enable it.
But I am not sure, maybe for HTTPS connection your need to use some SSL related AT command instead of your actual command that you are using for HTTP.

6

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