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ESP32 - HTTP Request
This tutorial instructs you how to use ESP32 to make HTTP request to web server, API, or Web service. In detail, You will learn:
- How to use ESP32 to make HTTP request (GET and POST)
- How to include the sensor's data into HTTP request
Hardware Used In This Tutorial
| 1 | × | ESP-WROOM-32 Dev Module | |
| 1 | × | Micro USB Cable | |
| 1 | × | (Optional) 5V Power Adapter | |
| 1 | × | (Optional) DC Power Jack | |
| 1 | × | (Optional) ESP32 Screw Terminal Adapter |
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Basic Concepts of Web Client and Web Server
There are some basic concepts of web such as: web address (URL), hostname, pathname, query string, HTTP Request... You can learn detailed about them in HTTP tutorial
How to Make an HTTP Request
- Declare request method, HTTP port, hostname, pathname, query string
const int HTTP_PORT = 80;
const String HTTP_METHOD = "GET"; // or "POST"
const char HOST_NAME[] = "google.com"; // hostname of web server:
const String PATH_NAME = "";
- Declare a web client object
- Connect to web server
if(client.connect(HOST_NAME, HTTP_PORT)) {
Serial.println("Connected to server");
} else {
Serial.println("connection failed");
}
- If connected to server, send HTTP request
// send HTTP request header
client.println(HTTP_METHOD + " " + PATH_NAME + " HTTP/1.1");
client.println("Host: " + String(HOST_NAME));
client.println("Connection: close");
client.println(); // end HTTP request header
- Read the response data from web server
while(client.available())
{
// read an incoming byte from the server and print them to serial monitor:
char c = client.read();
Serial.print(c);
}
if(!client.connected())
{
// if the server's disconnected, stop the client:
Serial.println("disconnected");
client.stop();
}
How to include data into HTTP request
We can send data to the web server by including data into HTTP request. The data format depends on HTTP request method:
- For HTTP GET request
- Data can be only sent in query string on the pathname.
- HTTP POST request
- Data can be sent NOT ONLY in query string format BUT ALSO any other format such as Json, XML, image ...
- Data is put in HTTP request body.
- Create a query string
- HTTP GET: add query string to pathname
- HTTP POST: put query string in HTTP body
- For both GET and POST, read the response data from web server
Let's learn how to send data in query string format for both HTTP GET and POST
int temp = // from sensor
int humi = // from sensor
String queryString = String("?temperature=") + String(temp) + String("&humidity=") + String(humi);
// send HTTP header
client.println("GET " + PATH_NAME + queryString + " HTTP/1.1");
client.println("Host: " + String(HOST_NAME));
client.println("Connection: close");
client.println(); // end HTTP header
// send HTTP header
client.println("POST " + PATH_NAME + " HTTP/1.1");
client.println("Host: " + String(HOST_NAME));
client.println("Connection: close");
client.println(); // end HTTP header
// send HTTP body
client.println(queryString);
while(client.available()) {
// read an incoming byte from the server and print them to serial monitor:
char c = client.read();
Serial.print(c);
}
if(!client.connected()) {
// if the server's disconnected, stop the client:
Serial.println("disconnected");
client.stop();
}
Complete ESP32 Code for Making HTTP Request
The blow is the complete ESP32 code for making HTTP GET/POST request
/*
* This ESP32 code is created by esp32io.com
*
* This ESP32 code is released in the public domain
*
* For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-http-request
*/
Complete ESP32 Code for Making HTTP GET Request with data
/*
* This ESP32 code is created by esp32io.com
*
* This ESP32 code is released in the public domain
*
* For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-http-request
*/
Complete ESP32 Code for Making HTTP POST Request with data
/*
* This ESP32 code is created by esp32io.com
*
* This ESP32 code is released in the public domain
*
* For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-http-request
*/
WARNING
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