esp8266/libraries/ESP8266WebServer/examples/WebUpdate/WebUpdate.ino

/*
  To upload through terminal you can use: curl -F "image=@firmware.bin" esp8266-webupdate.local/update
*/

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>

#ifndef STASSID
#define STASSID "your-ssid"
#define STAPSK "your-password"
#endif

const char* host = "esp8266-webupdate";
const char* ssid = STASSID;
const char* password = STAPSK;

ESP8266WebServer server(80);
const char* serverIndex = "<form method='POST' action='/update' enctype='multipart/form-data'><input type='file' name='update'><input type='submit' value='Update'></form>";

void setup(void) {
  Serial.begin(115200);
  Serial.println();
  Serial.println("Booting Sketch...");
  WiFi.mode(WIFI_AP_STA);
  WiFi.begin(ssid, password);
  if (WiFi.waitForConnectResult() == WL_CONNECTED) {
    MDNS.begin(host);
    server.on("/", HTTP_GET, []() {
      server.sendHeader("Connection", "close");
      server.send(200, "text/html", serverIndex);
    });
    server.on(
      "/update", HTTP_POST, []() {
        server.sendHeader("Connection", "close");
        server.send(200, "text/plain", (Update.hasError()) ? "FAIL" : "OK");
        ESP.restart();
      },
      []() {
        HTTPUpload& upload = server.upload();
        if (upload.status == UPLOAD_FILE_START) {
          Serial.setDebugOutput(true);
          WiFiUDP::stopAll();
          Serial.printf("Update: %s\n", upload.filename.c_str());
          uint32_t maxSketchSpace = (ESP.getFreeSketchSpace() - 0x1000) & 0xFFFFF000;
          if (!Update.begin(maxSketchSpace)) {  // start with max available size
            Update.printError(Serial);
          }
        } else if (upload.status == UPLOAD_FILE_WRITE) {
          if (Update.write(upload.buf, upload.currentSize) != upload.currentSize) {
            Update.printError(Serial);
          }
        } else if (upload.status == UPLOAD_FILE_END) {
          if (Update.end(true)) {  // true to set the size to the current progress
            Serial.printf("Update Success: %u\nRebooting...\n", upload.totalSize);
          } else {
            Update.printError(Serial);
          }
          Serial.setDebugOutput(false);
        }
        yield();
      });
    server.begin();
    MDNS.addService("http", "tcp", 80);

    Serial.printf("Ready! Open http://%s.local in your browser\n", host);
  } else {
    Serial.println("WiFi Failed");
  }
}

void loop(void) {
  server.handleClient();
  MDNS.update();
}