HTTP POST request to IFTTT

Question

I'm trying to send a POST request to IFTTT from a Node MCU. Instead of writing the code from the scratch, I've tweaked an already existing code (for GET request). It does not seem to work, what am I doing wrong? Needless to say, I replaced the WIFI ssid, the password and the IFTTT token. When testing the POST request with CURL, it works perfectly. Here's how the request should look like:

https://maker.ifttt.com/trigger/{event_name}/with/key/my_super_secret_token

...and the code:

#include <ESP8266WiFi.h>

const char* ssid     = "mywifi";
const char* password = "mywifipassword";

const char* host = "maker.ifttt.com";

void setup() {
  Serial.begin(115200);
  delay(100);

  // We start by connecting to a WiFi network

  Serial.println();
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("");
  Serial.println("WiFi connected");  
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

int value = 0;

void loop() {
  delay(5000);
  ++value;

  Serial.print("connecting to ");
  Serial.println(host);

  // Use WiFiClient class to create TCP connections
  WiFiClient client;
  const int httpPort = 80;
  if (!client.connect(host, httpPort)) {
    Serial.println("connection failed");
    return;
  }

  // We now create a URI for the request
  String url = "trigger/{trigga}/with/key/IFTTT_token";
  Serial.print("Requesting URL: ");
  Serial.println(url);

  // This will send the request to the server
client.print(String("POST ") + url + " HTTP/1.1\r\n" +
               "Host: " + host + "\r\n" + 
               "Connection: close\r\n\r\n");

    // Read all the lines of the reply from server and print them to Serial
  while(client.available()){
    String line = client.readStringUntil('\r');
    Serial.print(line);
  }

  Serial.println();
  Serial.println("closing connection");
}

Answer 1

Problem I see is that the request is incomplete - the server will be waiting for your payload.

client.print(String("POST ") + url + " HTTP/1.1\r\n" +
           "Host: " + host + "\r\n" + 
           "Connection: close\r\n\r\n");

You haven't specified a Content-Length header so the payload should start after the headers finish - but you don't send anything.

You need to (at least):

• add a payload or
• add a Content-Length: 0 header or
• add a payload with a matching Content-Length: header.

You can use curl to see a full set of valid POST headers like this:

curl -v -d "" http://localhost

You can use Chrome and Firefox's Web Inspector's Network tab to look at the raw headers of requests too.