How to send string to ESP32 using http

Question

My python code which should be sending the "message"

import requests
r = requests.post('http://192.168.0.100:7777',data="Hello")
print(r.text)

My ESP32 code, I think that the problem is caused because of wrong url, since I'm not sure what IP should I be using there. Is it the IP of the machine where the python code is running ? Or IP of ESP32 ? Or am I completely wrong ?

#include <WiFi.h>
#include <HTTPClient.h>
#include <WebServer.h>

WebServer server(7777);
HTTPClient http;

const char* ssid = "SSID";
const char* password =  "PASSWORD";

void handleRoot() {
  server.send(200, "text/plain", "Hello World!");
}

void handleNotFound() {
  server.send(404, "text/plain", "Hello World!");
}

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

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    Serial.println("Connecting to WiFi..");
  }
  Serial.println(WiFi.localIP());

  server.on("/", handleRoot);
  server.onNotFound(handleNotFound);
  server.begin();
  http.begin("http://192.168.0.100/");
}

void loop() {
 server.handleClient();
 int httpCode = http.GET();
 String payload = http.getString();
 Serial.println(httpCode);
 Serial.println(payload);
}

EDIT: Now the ESP should act as a server

Answer 1

When you send a GET/POST request you must put the IP of the destination, in this case, the IP of your ESP32.

First thing to note, my server.begin() was listening on 192.168.4.1:80 by default as an access point.

Now, to create an asynchronous server that holds GET and POST requests with json data you can have a function like this:

file http_server.h:

#include "WiFi.h"
#include "ESPAsyncWebServer.h"
#include "ArduinoJson.h"

#ifndef _HTTP_SERVER_
#define _HTTP_SERVER_

void setup_http_server();

#endif

example of file http_server.cpp:

#include "http_server.h"

AsyncWebServer server(80);  // start server listening on port 80
void setup_http_server(){

    // Example of function that holds and HTTP_GET request on 192.168.4.1:80/get_data
    server.on("/get_data", HTTP_GET, [](AsyncWebServerRequest *request){
        // Code that holds the request
        Serial.println("Get received"); // Just for debug
        request->send(HTTP_200_code, "text/plain", "Here I am"); 
    });

    // Example of function that holds and HTTP_POST request on 192.168.4.1:80/set_data
    server.on("/set_data",
        HTTP_POST,
        [](AsyncWebServerRequest * request){},
        NULL,
        [](AsyncWebServerRequest * request, uint8_t *data, size_t len,
        size_t index, size_t total) {
            // Here goes the code to manage the post request
            // The data is received on 'data' variable
            // Parse data
            Serial.printlnt("POST RECEIVED"); // Just for debug
            StaticJsonBuffer<50> JSONBuffer; // create a buffer that fits for you
            JsonObject& parsed = JSONBuffer.parseObject(data); //Parse message
            uint8_t received_data = parsed["number"]; //Get data
            request->send(HTTP_200_code, "text/plain", "Some message");
    });

    server.begin();  // starts asyncrhonus controller
    Serial.println(WiFi.softAPIP());  // you can print you IP yo be sure that it is 192.168.4.1
}

Finally, if you want to conect directly to your ESP32 with your mobile/computer, you will need to configure its wifi connection as an ACCESS_POINT. So, your setup() and loop()in your main.ino could look like:

file main.ino:

#include "http_server.h"

void setup(){
     Serial.begin(9600);  // setup serial communication
     // Set WiFi to station(STA) and access point (AP) mode simultaneously 
     WiFi.mode(WIFI_AP_STA);
     delay(100); // Recommended delay
     WiFi.softAP("choose_some_ssid", "choose_some_password");

     // Remember to configure the previous server
     setup_http_server();  // starts the asyncronus https server*/
}

void loop(){
     delay(1000);
}

And that's all. to check that everything worked you can connect your mobile phone to the wifi choose_some_ssid with password chose_some_password, open a browser and go to 192.168.4.1/get_data and you should get "Here I am" as response.

As you said on your question, if you want to send a post with python you can do:

import requests
r = requests.post('http://192.168.4.1:80/set_data', data="{'number':55}") // remember that you get the keyword 'number' in the server side
print(r.text) // should print "Some message"

More information can be found on https://techtutorialsx.com/2018/10/12/esp32-http-web-server-handling-body-data/ Hope it helps!