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();

    });