HTTP post via GPRS (SIM808) to Azure http endpoint logic app is failing

Question

I am using a SIM808 with a atmega2560.

I have setup the endpoint in Azure and that works when I try a http post via postman and/or an online http post tool (I get a 202 as result and see data comming into Azure)

I want to send a json package to an Azure http endpoint (smart app) using the function httpPOST in the SIMCom library from itead.

I am connecting to the network:

logging (I printed all that is written to GSM):

AT+CIFSR
DB:STARTING NEW CONNECTION
AT+CIPSHUT
DB:SHUTTED OK
AT+CSTT="provider.net","","" DB:APN OK
AT+CIICR
DB:CONNECTION OK
AT+CIFSR
DB:ASSIGNED AN IP
GPRS status=ATTACHED
AT+CIPSTART="TCP","prod-13.westeurope.logic.azure.com",443
DB:RECVD CMD
DB:OK TCP

Then call the httpPost function from the library with the following variables:

const char server[35] = "prod-13.westeurope.logic.azure.com";
const int port = 443;
const char path[200] = "/workflows/someazureID/triggers/manual/paths/invoke?api-version=2016年10月01日&sp=%2Ftriggers%2Fmanual%2Frun&sv=1.0&sig=someazuretoken";
const char parameters[100] = "{\"device\":\"alive\",\"timestamp\":\"09270845\"}";

Part of the httpPost function from the library for sending the data

 int InetGSM::httpPOST(const char* server, int port, const char* path, const char* parameters, char* result, int resultlength)
 ....
 gsm.SimpleWrite("POST ");
 gsm.SimpleWrite(path);
 gsm.SimpleWrite(" HTTP/1.1\r\nHost: ");
 gsm.SimpleWrite(server);
 gsm.SimpleWrite("\r\n");
 gsm.SimpleWrite("User-Agent: Arduino\r\n");
 gsm.SimpleWrite("Content-Type: application/json\r\n");
 gsm.SimpleWrite("Content-Length: ");
 itoa(strlen(parameters),itoaBuffer,10);
 gsm.SimpleWrite(itoaBuffer);
 gsm.SimpleWrite("\r\n\r\n");
 gsm.SimpleWrite(parameters);
 gsm.SimpleWrite("\r\n\r\n");
 gsm.SimpleWrite(end_c);
....

Which gives this output on the serial monitor (I printed all that is written to GSM):

AT+CIPSEND
DB:>
POST /workflows/someazureID/triggers/manual/paths/invoke?api-version=2016年10月01日&sp=%2Ftriggers%2Fmanual%2Frun&sv=1.0&sig=someazuretoken HTTP/1.1
Host: prod-13.westeurope.logic.azure.com
User-Agent: Arduino
Content-Type: application/json
Content-Length: 55
{"device":"alive","timestamp":"09270845"}
DB:SENT

And then it is waiting for a response:

Starting read..
Waiting for Data............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 
CLOSED 
Done..
response:
10
CLOSED

which times out I guess.

And I see nothing coming into Azure.

(I am getting data when I try a httpGet on a random site. So hardware, sim and network is working ok I guess)

Any ideas? thx!

• Juraj: doesn't Azure use https?
• Jeroen: yes it does, I am connecting to port 443 'const char server[35] = "prod-13.westeurope.logic.azure.com"; const int port = 443;' But honestly I have never done this before so maybe I am forgetting/missing something
• Juraj: I don't know the AT commands for the GSM module, but it doesn't look like you would handle SSL

Answer 1

Juraj's comments put me on the right track, for SSL you need to do more then just select the port.

I did some searching and got it to work using a different GSM library that also supports SSL: tinyGSM

in combination with ArduinoHttpClient

Jeroen

EDIT: It works, but there is a big downside. It looks like there is major overhead, each message seems to uses 13Kb of data...? I suspect this comes from the data that is returned by the endpoint. This is way too much over GPRS so now looking into MQTT.