Format for HTTP request using AT commands in SLM application

[Shivek]

Hi,

I am  trying to retrieve data from server using HTTP GET request, using AT command for Serial LTE modem application.

So, I can connect to the server using AT#XHTTPCCON command, but not able to get the data from the server. Here is the format for HTTP request I am sending to the nRF91600 over UART using nRF Connect v 3.7.0.

AT#XHTTPCREQ="GET","/instruments/150771004/temperature-values/?page=1 HTTP/1.1","Host: demo.abc.com\r\nAccept: application/vnd.api+json\r\nAuthorization: Basic ZGVtbzpkZxxx\r\n"

I put abc.com and xxx here in the Host and Authorization fields just because of company policy. 

The server is responding with 400 bad request error.

Can you please let me know if I am missing something in the header field format?

I have checked on the server side, and I can see upto the resource field (up to HTTP/1.1), its in correct format. So, I am guessing there is something to do with header field of the command.

I couldn't find any example from Nordic what should be the format if there is any header field in the HTTP request, i.e., for authorization etc.

I tried to get the SLM application in debug mode and I could see its getting the proper string for httpc.headers variable in handle_AT_HTTPC_REQUEST function of the slm_at_httpc.c source file.

I am using nRF Connect v 3.7.0, nRF Connect SDK v1.4.1, in software tools and nRF9160DK for the hardware.

Looking forward for a prompt response.

Regards,

Shivek

[Albrecht Markus Schellenberger]

Hello Shivek,

Only in C language "\r\n" is understood as <CR><LF>. HTTP payload is sent as raw data so there should be raw CR and LF, which in your case should look like this:

AT#XHTTPCREQ="GET","/instruments/150771004/temperature-values/?page=1 HTTP/1.1","Host: demo.abc.com
Accept: application/vnd.api+json
Authorization: Basic ZGVtbzpkZxxx
"

The following example in the SLM documentation demonstrates the usage as well. I hope this will solve your issue!

Regards,

Markus

[Shivek]

Thanks for your response Markus, but I already have tried with hex values for nrf Link monitor i.e., \x0D for <CR> and \x0A for <LF>. And it understand those very well. I am saying that because I can see on the console screen. So, for the command below

AT#XHTTPCREQ="GET","/instruments/150771004/temperature-values/?page=1  HTTP/1.1","Host: demo.abc.com\x0D\x0AAccept: application/vnd.api+json\x0D\x0AAuthorization: Basic ZGVtbzpkZxxx\x0D\x0A"

It shows like this:

AT#XHTTPCREQ="GET","/instruments/150771004/temperature-values/?page=1  HTTP/1.1","Host: demo.abc.com

Accept: application/vnd.api+json

Authorization: Basic ZGVtbzpkZxxx

"

This I have copied and pasted from the console in Link Monitor app after the command is sent. 

Would you please give me some demo using Link monitor for a HTTP request incorporating more than one header fields?
That would be really helpful as I would be able to see what exactly has to be done. 

Regards,
Shivek