ResumableDownload.ino

// SPDX-License-Identifier: LGPL-3.0-or-later
// Copyright 2016-2026 Hristo Gochkov, Mathieu Carbou, Emil Muratov, Will Miles

//
// Make sure resumable downloads can be implemented (HEAD request / response and Range header)
//

#include <Arduino.h>
#if defined(ESP32) || defined(LIBRETINY)
#include <AsyncTCP.h>
#include <WiFi.h>
#elif defined(ESP8266)
#include <ESP8266WiFi.h>
#include <ESPAsyncTCP.h>
#elif defined(TARGET_RP2040) || defined(TARGET_RP2350) || defined(PICO_RP2040) || defined(PICO_RP2350)
#include <RPAsyncTCP.h>
#include <WiFi.h>
#endif

#include <ESPAsyncWebServer.h>

static AsyncWebServer server(80);

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

#if ASYNCWEBSERVER_WIFI_SUPPORTED
  WiFi.mode(WIFI_AP);
  WiFi.softAP("esp-captive");
#endif

  /*
    ❯ curl -I -X HEAD http://192.168.4.1/download
    HTTP/1.1 200 OK
    Content-Length: 1024
    Content-Type: application/octet-stream
    Connection: close
    Accept-Ranges: bytes
  */
  // Ref: https://github.com/mathieucarbou/ESPAsyncWebServer/pull/80
  server.on("/download", HTTP_HEAD | HTTP_GET, [](AsyncWebServerRequest *request) {
    if (request->method() == HTTP_HEAD) {
      AsyncWebServerResponse *response = request->beginResponse(200, "application/octet-stream");
      response->addHeader(asyncsrv::T_Accept_Ranges, "bytes");
      response->addHeader(asyncsrv::T_Content_Length, 10);
      response->setContentLength(1024);  // make sure we can overrides previously set content length
      response->addHeader(asyncsrv::T_Content_Type, "foo");
      response->setContentType("application/octet-stream");  // make sure we can overrides previously set content type
      // ...
      request->send(response);
    } else {
      // ...
    }
  });

  server.begin();
}

void loop() {
  delay(100);
}