ESP32: How to create an Over-The-Air (OTA) Web Update

				
					#include <WiFi.h>
#include <WebServer.h>
#include <Update.h>
#include <ESPmDNS.h> // For accessing the board by hostname (e.g., http://esp32.local)

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

// Define hostname for mDNS
const char* host = "esp32"; 

// Initialize the WebServer on HTTP port 80
WebServer server(80);

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

  // Connect to Wi-Fi
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  while (WiFi.waitForConnectResult() != WL_CONNECTED) {
    Serial.println("Connection Failed! Rebooting...");
    delay(5000);
    ESP.restart();
  }
  
  // Start mDNS service for easier access
  if(MDNS.begin(host)) {
    Serial.println("mDNS responder started");
  }

  Serial.println("\nWiFi connected.");
  Serial.print("Access OTA at: http://");
  Serial.print(host);
  Serial.println(".local/update");
  Serial.print("Or by IP: http://");
  Serial.print(WiFi.localIP());
  Serial.println("/update");

  // 1. Setup routes
  server.on("/", HTTP_GET, [](){ server.send(200, "text/plain", "Firmware V1.0. Use /update to upload new firmware."); });
  server.on("/update", HTTP_GET, handleRoot);
  server.on("/update", HTTP_POST, [](){
    server.sendHeader("Connection", "close");
    server.send(200, "text/plain", (Update.hasError()) ? "FAIL" : "OK");
    ESP.restart();
  }, handleUpdate);

  // 2. Start the server
  server.begin();
}

void handleRoot() {
  server.send(200, "text/html", "<form method='POST' action='/update' enctype='multipart/form-data'>"
                               "<input type='file' name='firmware'>"
                               "<input type='submit' value='Update Firmware'></form>");
}

void handleUpdate() {
  HTTPUpload& upload = server.upload();
  
  if (upload.status == UPLOAD_FILE_START) {
    Serial.printf("Update: Starting file: %s\n", upload.filename.c_str());
    
    // Check if the firmware file size exceeds the available OTA space
    if (!Update.begin(UPDATE_SIZE_UNKNOWN)) { 
      Update.printError(Serial);
    }
  } else if (upload.status == UPLOAD_FILE_WRITE) {
    // Write received data to the flash memory
    if (Update.write(upload.buf, upload.currentSize) != upload.currentSize) {
      Update.printError(Serial);
    }
  } else if (upload.status == UPLOAD_FILE_END) {
    // Finalize the update and verify checksum
    if (Update.end(true)) { 
      Serial.printf("Update Success: %u bytes written.\nRebooting now...", upload.totalSize);
    } else {
      Update.printError(Serial);
    }
  }
}

void loop() {
  server.handleClient();
  //MDNS.update();
  // No deep logic needed here, as the web server handles all requests.
}