Looking for a working sample code for how to send HTTP POST requests.

[vt-vaio]

I need to send a post request via HTTP with JSON in the request body. I was trying to use httpSend() but always getting a 400 response from the backend. For me it looks like that JSON string is never transmitted as part of the request. I can reproduce the same 400 error with Postman when removing the JSON string from the body.

Below is a code snipped from my tests (the backend and API endpoints are replaced with placeholders).

    if(m_modem->httpConfigProfile(1, "my-backend")) {
        debug_out("Successfully configured the http profile");
    } 
    else {
        debug_out("Failed to configure HTTP profile");
        return;
    }

    std::string smsg = "{'id':'240ac4c6f33c','fw_version':'3.0'}";
    const uint8_t *msg = reinterpret_cast<const uint8_t*>(smsg.c_str());

    bool sent = m_modem->httpSend(1, "/my-endpoint", (uint8_t *) msg, sizeof(msg), WALTER_MODEM_HTTP_SEND_CMD_POST, WALTER_MODEM_HTTP_POST_PARAM_JSON);

    if(sent) {
        debug_out("Request successfully sent");

        delay(5000);

        debug_out("Looking for reply");

        WalterModemRsp *rsp = new WalterModemRsp();

        uint8_t incomingBuf[256] = { 0 };

        while(m_modem->httpDidRing(1, incomingBuf, sizeof(incomingBuf), rsp)) {
            esp_task_wdt_reset();
            debug_out("HTTP status code: " + String(rsp->data.httpResponse.httpStatus));
            Serial.printf("[%s]\r\n", incomingBuf);
        }

        debug_out("Stooped looking for reply");
    } 

Below is some debug output

TX: AT+SQNHTTPCFG=1,"my-backend",80,0,"","" RX: OK TX: AT+SQNHTTPSND=1,0,"/my-endpoint",4,"4" RX: > RX: OK RX: +SQNHTTPRING: 1,400,"text/html; charset=UTF-8",0 TX: AT+SQNHTTPRCV=1 RX: +CME ERROR: 587 TX: AT+SQNHTTPRCV=1 RX: +CME ERROR: 587 TX: AT+SQNHTTPRCV=1 RX: +CME ERROR: 587

[vt-vaio]

I've sorted the issue. My problem was in the the 4th parameter (dataSize). The sizeof always returned 4. By changing the code in the following way all works now.

    std::string smsg = "{'id':'240ac4c6f33c','fw_version':'3.0'}";
    const uint8_t *msg = reinterpret_cast<const uint8_t*>(smsg.c_str());

    bool sent = m_modem->httpSend(1, "/my-endpoint", (uint8_t *) msg, smsg.length(), WALTER_MODEM_HTTP_SEND_CMD_POST, WALTER_MODEM_HTTP_POST_PARAM_JSON);

[vt-vaio]

Solved, please see my previous comment for solution. Thank you.