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");
}

• Gerben: Don't you need to send any actual data in the body of the POST request? Do you get any output on the serial console?
• alkopop79: I get nothing on the serial console, not even error code. I don't think my request goes through at all.
• alkopop79: @Gerben, Not sure about sending data. IFTTT recipes do not expect data. That's what they say: Make a POST or GET web request to: maker.ifttt.com/trigger{event}/with/key/my_super_secret_token With an optional JSON body of: { "value1" : "", "value2" : "", "value3" : "" } The data is completely optional, and you can also pass value1, value2, and value3 as query parameters or form variables. This content will be passed on to the Action in your Recipe.
• alkopop79: I'm still not sure how to make this work but this one (with GET method) works nicely: bigjungle.net/blog/2015/6/26/connect-maker-to-anything-ifttt
• SoreDakeNoKoto: When you say you get nothing in the serial monitor, does that include the Serial.print()s in setup()? Nothing at all shows when you run the sketch? Perhaps its a baud rate issue? How is the ESP connected to the Node MCU?

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.