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]

Thanks a lot for your feedback, Shivek!

Shivek said:

And it understand those very well.

Yes, the LTE Link Monitor should convert this to the right raw data format.

Could you remove the "HTTP/1.1" part and check if that makes any difference?

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

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

I would strongly recommend update to at least NCS v1.5.0. There is some instability with the SLM application in earlier versions.

Regards,

Markus

[Shivek]

Hi Markus,

Albrecht Markus Schellenberger said:

Could you remove the "HTTP/1.1" part and check if that makes any difference?

I already have tried removing HTTP/1.1. That also didn't work.

Albrecht Markus Schellenberger said:

I would strongly recommend update to at least NCS v1.5.0

I tried with NCS v1.6.1, its the same 400 Bad request error I am getting.

Would you be able to send me some example having more than one header fields as in my case, i.e., authentication, host etc.?

I have tried debugging using SES and I could see the httpc.headers field was getting correct header string from the command. I stopped the program just before calling http_client_req() function. Here is the snapshot from debugging window:

 

I can see the method, and header fields of the HTTP request are traversed by the application correctly.

I would appreciate any insight on this.

Regards,

Shivek