examples/SimpleServer/SimpleServer.ino

//
// A simple server implementation showing how to:
//  * serve static messages
//  * read GET and POST parameters
//  * handle missing pages / 404s
//

#include <Arduino.h>
#ifdef ESP32
  #include <AsyncTCP.h>
  #include <WiFi.h>
#elif defined(ESP8266)
  #include <ESP8266WiFi.h>
  #include <ESPAsyncTCP.h>
#elif defined(TARGET_RP2040)
  #include <WebServer.h>
  #include <WiFi.h>
#endif

#include <ESPAsyncWebServer.h>

#if __has_include("ArduinoJson.h")
  #include <ArduinoJson.h>
  #include <AsyncJson.h>
  #include <AsyncMessagePack.h>
#endif

#include <LittleFS.h>

const char* htmlContent PROGMEM = R"(
<!DOCTYPE html>
<html>
<head>
    <title>Sample HTML</title>
</head>
<body>
    <h1>Hello, World!</h1>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin euismod, purus a euismod
    rhoncus, urna ipsum cursus massa, eu dictum tellus justo ac justo. Quisque ullamcorper
    arcu nec tortor ullamcorper, vel fermentum justo fermentum. Vivamus sed velit ut elit
    accumsan congue ut ut enim. Ut eu justo eu lacus varius gravida ut a tellus. Nulla facilisi.
    Integer auctor consectetur ultricies. Fusce feugiat, mi sit amet bibendum viverra, orci leo
    dapibus elit, id varius sem dui id lacus.</p>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin euismod, purus a euismod
    rhoncus, urna ipsum cursus massa, eu dictum tellus justo ac justo. Quisque ullamcorper
    arcu nec tortor ullamcorper, vel fermentum justo fermentum. Vivamus sed velit ut elit
    accumsan congue ut ut enim. Ut eu justo eu lacus varius gravida ut a tellus. Nulla facilisi.
    Integer auctor consectetur ultricies. Fusce feugiat, mi sit amet bibendum viverra, orci leo
    dapibus elit, id varius sem dui id lacus.</p>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin euismod, purus a euismod
    rhoncus, urna ipsum cursus massa, eu dictum tellus justo ac justo. Quisque ullamcorper
    arcu nec tortor ullamcorper, vel fermentum justo fermentum. Vivamus sed velit ut elit
    accumsan congue ut ut enim. Ut eu justo eu lacus varius gravida ut a tellus. Nulla facilisi.
    Integer auctor consectetur ultricies. Fusce feugiat, mi sit amet bibendum viverra, orci leo
    dapibus elit, id varius sem dui id lacus.</p>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin euismod, purus a euismod
    rhoncus, urna ipsum cursus massa, eu dictum tellus justo ac justo. Quisque ullamcorper
    arcu nec tortor ullamcorper, vel fermentum justo fermentum. Vivamus sed velit ut elit
    accumsan congue ut ut enim. Ut eu justo eu lacus varius gravida ut a tellus. Nulla facilisi.
    Integer auctor consectetur ultricies. Fusce feugiat, mi sit amet bibendum viverra, orci leo
    dapibus elit, id varius sem dui id lacus.</p>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin euismod, purus a euismod
    rhoncus, urna ipsum cursus massa, eu dictum tellus justo ac justo. Quisque ullamcorper
    arcu nec tortor ullamcorper, vel fermentum justo fermentum. Vivamus sed velit ut elit
    accumsan congue ut ut enim. Ut eu justo eu lacus varius gravida ut a tellus. Nulla facilisi.
    Integer auctor consectetur ultricies. Fusce feugiat, mi sit amet bibendum viverra, orci leo
    dapibus elit, id varius sem dui id lacus.</p>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin euismod, purus a euismod
    rhoncus, urna ipsum cursus massa, eu dictum tellus justo ac justo. Quisque ullamcorper
    arcu nec tortor ullamcorper, vel fermentum justo fermentum. Vivamus sed velit ut elit
    accumsan congue ut ut enim. Ut eu justo eu lacus varius gravida ut a tellus. Nulla facilisi.
    Integer auctor consectetur ultricies. Fusce feugiat, mi sit amet bibendum viverra, orci leo
    dapibus elit, id varius sem dui id lacus.</p>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin euismod, purus a euismod
    rhoncus, urna ipsum cursus massa, eu dictum tellus justo ac justo. Quisque ullamcorper
    arcu nec tortor ullamcorper, vel fermentum justo fermentum. Vivamus sed velit ut elit
    accumsan congue ut ut enim. Ut eu justo eu lacus varius gravida ut a tellus. Nulla facilisi.
    Integer auctor consectetur ultricies. Fusce feugiat, mi sit amet bibendum viverra, orci leo
    dapibus elit, id varius sem dui id lacus.</p>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin euismod, purus a euismod
    rhoncus, urna ipsum cursus massa, eu dictum tellus justo ac justo. Quisque ullamcorper
    arcu nec tortor ullamcorper, vel fermentum justo fermentum. Vivamus sed velit ut elit
    accumsan congue ut ut enim. Ut eu justo eu lacus varius gravida ut a tellus. Nulla facilisi.
    Integer auctor consectetur ultricies. Fusce feugiat, mi sit amet bibendum viverra, orci leo
    dapibus elit, id varius sem dui id lacus.</p>
</body>
</html>
)";

const size_t htmlContentLength = strlen_P(htmlContent);

const char* staticContent PROGMEM = R"(
<!DOCTYPE html>
<html>
<head>
    <title>Sample HTML</title>
</head>
<body>
    <h1>Hello, %IP%</h1>
</body>
</html>
)";

AsyncWebServer server(80);
AsyncEventSource events("/events");
AsyncWebSocket ws("/ws");

/////////////////////////////////////////////////////////////////////////////////////////////////////
// Middlewares
/////////////////////////////////////////////////////////////////////////////////////////////////////

// log incoming requests
AsyncLoggingMiddleware requestLogger;

// CORS
AsyncCorsMiddleware cors;

// maximum 5 requests per 10 seconds
AsyncRateLimitMiddleware rateLimit;

// filter out specific headers from the incoming request
AsyncHeaderFilterMiddleware headerFilter;

// remove all headers from the incoming request except the ones provided in the constructor
AsyncHeaderFreeMiddleware headerFree;

// basicAuth
AsyncAuthenticationMiddleware basicAuth;
AsyncAuthenticationMiddleware basicAuthHash;

// simple digest authentication
AsyncAuthenticationMiddleware digestAuth;
AsyncAuthenticationMiddleware digestAuthHash;

// complex authentication which adds request attributes for the next middlewares and handler
AsyncMiddlewareFunction complexAuth([](AsyncWebServerRequest* request, ArMiddlewareNext next) {
  if (!request->authenticate("user", "password")) {
    return request->requestAuthentication();
  }
  request->setAttribute("user", "Mathieu");
  request->setAttribute("role", "staff");

  next();

  request->getResponse()->addHeader("X-Rate-Limit", "200");
});

AsyncAuthorizationMiddleware authz([](AsyncWebServerRequest* request) { return request->getAttribute("role") == "staff"; });

int wsClients = 0;

/////////////////////////////////////////////////////////////////////////////////////////////////////

const char* PARAM_MESSAGE PROGMEM = "message";
const char* SSE_HTLM PROGMEM = R"(
<!DOCTYPE html>
<html>
<head>
  <title>Server-Sent Events</title>
  <script>
    if (!!window.EventSource) {
      var source = new EventSource('/events');
      source.addEventListener('open', function(e) {
        console.log("Events Connected");
      }, false);
      source.addEventListener('error', function(e) {
        if (e.target.readyState != EventSource.OPEN) {
          console.log("Events Disconnected");
        }
      }, false);
      source.addEventListener('message', function(e) {
        console.log("message", e.data);
      }, false);
      source.addEventListener('heartbeat', function(e) {
        console.log("heartbeat", e.data);
      }, false);
    }
  </script>
</head>
<body>
  <h1>Open your browser console!</h1>
</body>
</html>
)";

void notFound(AsyncWebServerRequest* request) {
  request->send(404, "text/plain", "Not found");
}

#if __has_include("ArduinoJson.h")
AsyncCallbackJsonWebHandler* jsonHandler = new AsyncCallbackJsonWebHandler("/json2");
AsyncCallbackMessagePackWebHandler* msgPackHandler = new AsyncCallbackMessagePackWebHandler("/msgpack2");
#endif

static const char characters[] = "0123456789ABCDEF";
static size_t charactersIndex = 0;

void setup() {

  Serial.begin(115200);

#ifndef CONFIG_IDF_TARGET_ESP32H2
  // WiFi.mode(WIFI_STA);
  // WiFi.begin("YOUR_SSID", "YOUR_PASSWORD");
  // if (WiFi.waitForConnectResult() != WL_CONNECTED) {
  //   Serial.printf("WiFi Failed!\n");
  //   return;
  // }
  // Serial.print("IP Address: ");
  // Serial.println(WiFi.localIP());

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

#ifdef ESP32
  LittleFS.begin(true);
#else
  LittleFS.begin();
#endif

  {
    File f = LittleFS.open("/index.txt", "w");
    if (f) {
      for (size_t c = 0; c < sizeof(characters); c++) {
        for (size_t i = 0; i < 1024; i++) {
          f.print(characters[c]);
        }
      }
      f.close();
    }
  }

  {
    File f = LittleFS.open("/index.html", "w");
    if (f) {
      f.print(staticContent);
      f.close();
    }
  }

  // curl -v -X GET http://192.168.4.1/handler-not-sending-response
  server.on("/handler-not-sending-response", HTTP_GET, [](AsyncWebServerRequest* request) {
    // handler forgot to send a response to the client => 501 Not Implemented
  });

  // This is possible to replace a response.
  // the previous one will be deleted.
  // response sending happens when the handler returns.
  // curl -v -X GET http://192.168.4.1/replace
  server.on("/replace", HTTP_GET, [](AsyncWebServerRequest* request) {
    request->send(200, "text/plain", "Hello, world");
    // oups! finally we want to send a different response
    request->send(400, "text/plain", "validation error");
#ifndef TARGET_RP2040
    Serial.printf("Free heap: %" PRIu32 "\n", ESP.getFreeHeap());
#endif
  });

  ///////////////////////////////////////////////////////////////////////
  // Request header manipulations
  ///////////////////////////////////////////////////////////////////////

  // curl -v -X GET -H "x-remove-me: value" http://192.168.4.1/headers
  server.on("/headers", HTTP_GET, [](AsyncWebServerRequest* request) {
    Serial.printf("Request Headers:\n");
    for (auto& h : request->getHeaders())
      Serial.printf("Request Header: %s = %s\n", h.name().c_str(), h.value().c_str());

    // remove x-remove-me header
    request->removeHeader("x-remove-me");
    Serial.printf("Request Headers:\n");
    for (auto& h : request->getHeaders())
      Serial.printf("Request Header: %s = %s\n", h.name().c_str(), h.value().c_str());

    std::vector<const char*> headers;
    request->getHeaderNames(headers);
    for (auto& h : headers)
      Serial.printf("Request Header Name: %s\n", h);

    request->send(200);
  });

  ///////////////////////////////////////////////////////////////////////
  // Middlewares at server level (will apply to all requests)
  ///////////////////////////////////////////////////////////////////////

  requestLogger.setOutput(Serial);

  basicAuth.setUsername("admin");
  basicAuth.setPassword("admin");
  basicAuth.setRealm("MyApp");
  basicAuth.setAuthFailureMessage("Authentication failed");
  basicAuth.setAuthType(AsyncAuthType::AUTH_BASIC);
  basicAuth.generateHash();

  basicAuthHash.setUsername("admin");
  basicAuthHash.setPasswordHash("YWRtaW46YWRtaW4="); // BASE64(admin:admin)
  basicAuthHash.setRealm("MyApp");
  basicAuthHash.setAuthFailureMessage("Authentication failed");
  basicAuthHash.setAuthType(AsyncAuthType::AUTH_BASIC);

  digestAuth.setUsername("admin");
  digestAuth.setPassword("admin");
  digestAuth.setRealm("MyApp");
  digestAuth.setAuthFailureMessage("Authentication failed");
  digestAuth.setAuthType(AsyncAuthType::AUTH_DIGEST);
  digestAuth.generateHash();

  digestAuthHash.setUsername("admin");
  digestAuthHash.setPasswordHash("f499b71f9a36d838b79268e145e132f7"); // MD5(user:realm:pass)
  digestAuthHash.setRealm("MyApp");
  digestAuthHash.setAuthFailureMessage("Authentication failed");
  digestAuthHash.setAuthType(AsyncAuthType::AUTH_DIGEST);

  rateLimit.setMaxRequests(5);
  rateLimit.setWindowSize(10);

  headerFilter.filter("X-Remove-Me");
  headerFree.keep("X-Keep-Me");
  headerFree.keep("host");

  cors.setOrigin("http://192.168.4.1");
  cors.setMethods("POST, GET, OPTIONS, DELETE");
  cors.setHeaders("X-Custom-Header");
  cors.setAllowCredentials(false);
  cors.setMaxAge(600);

#ifndef PERF_TEST
  // global middleware
  server.addMiddleware(&requestLogger);
  server.addMiddlewares({&rateLimit, &cors, &headerFilter});
#endif

  // Test CORS preflight request
  // curl -v -X OPTIONS -H "origin: http://192.168.4.1" http://192.168.4.1/middleware/cors
  server.on("/middleware/cors", HTTP_GET, [](AsyncWebServerRequest* request) {
    request->send(200, "text/plain", "Hello, world!");
  });

  // curl -v -X GET -H "x-remove-me: value" http://192.168.4.1/middleware/test-header-filter
  // - requestLogger will log the incoming headers (including x-remove-me)
  // - headerFilter will remove x-remove-me header
  // - handler will log the remaining headers
  server.on("/middleware/test-header-filter", HTTP_GET, [](AsyncWebServerRequest* request) {
    for (auto& h : request->getHeaders())
      Serial.printf("Request Header: %s = %s\n", h.name().c_str(), h.value().c_str());
    request->send(200);
  });

  // curl -v -X GET -H "x-keep-me: value" http://192.168.4.1/middleware/test-header-free
  // - requestLogger will log the incoming headers (including x-keep-me)
  // - headerFree will remove all headers except x-keep-me and host
  // - handler will log the remaining headers (x-keep-me and host)
  server.on("/middleware/test-header-free", HTTP_GET, [](AsyncWebServerRequest* request) {
          for (auto& h : request->getHeaders())
            Serial.printf("Request Header: %s = %s\n", h.name().c_str(), h.value().c_str());
          request->send(200);
        })
    .addMiddleware(&headerFree);

  // basic authentication method
  // curl -v -X GET -H "origin: http://192.168.4.1" -u admin:admin  http://192.168.4.1/middleware/auth-basic
  server.on("/middleware/auth-basic", HTTP_GET, [](AsyncWebServerRequest* request) {
          request->send(200, "text/plain", "Hello, world!");
        })
    .addMiddleware(&basicAuth);

  // basic authentication method with hash
  // curl -v -X GET -H "origin: http://192.168.4.1" -u admin:admin  http://192.168.4.1/middleware/auth-basic-hash
  server.on("/middleware/auth-basic-hash", HTTP_GET, [](AsyncWebServerRequest* request) {
          request->send(200, "text/plain", "Hello, world!");
        })
    .addMiddleware(&basicAuthHash);

  // digest authentication
  // curl -v -X GET -H "origin: http://192.168.4.1" -u admin:admin --digest  http://192.168.4.1/middleware/auth-digest
  server.on("/middleware/auth-digest", HTTP_GET, [](AsyncWebServerRequest* request) {
          request->send(200, "text/plain", "Hello, world!");
        })
    .addMiddleware(&digestAuth);

  // digest authentication with hash
  // curl -v -X GET -H "origin: http://192.168.4.1" -u admin:admin --digest  http://192.168.4.1/middleware/auth-digest-hash
  server.on("/middleware/auth-digest-hash", HTTP_GET, [](AsyncWebServerRequest* request) {
          request->send(200, "text/plain", "Hello, world!");
        })
    .addMiddleware(&digestAuthHash);

  // test digest auth with cors
  // curl -v -X GET -H "origin: http://192.168.4.1" --digest -u user:password  http://192.168.4.1/middleware/auth-custom
  server.on("/middleware/auth-custom", HTTP_GET, [](AsyncWebServerRequest* request) {
          String buffer = "Hello ";
          buffer.concat(request->getAttribute("user"));
          buffer.concat(" with role: ");
          buffer.concat(request->getAttribute("role"));
          request->send(200, "text/plain", buffer);
        })
    .addMiddlewares({&complexAuth, &authz});

  ///////////////////////////////////////////////////////////////////////

  // curl -v -X GET -H "origin: http://192.168.4.1" http://192.168.4.1/redirect
  // curl -v -X POST -H "origin: http://192.168.4.1" http://192.168.4.1/redirect
  server.on("/redirect", HTTP_GET | HTTP_POST, [](AsyncWebServerRequest* request) {
    request->redirect("/");
  });

  // PERF TEST:
  // > brew install autocannon
  // > autocannon -c 10 -w 10 -d 20 http://192.168.4.1
  // > autocannon -c 16 -w 16 -d 20 http://192.168.4.1
  server.on("/", HTTP_GET, [](AsyncWebServerRequest* request) {
    request->send(200, "text/html", htmlContent);
  });

  // curl -v -X GET http://192.168.4.1/index.txt
  server.serveStatic("/index.txt", LittleFS, "/index.txt");

  // curl -v -X GET http://192.168.4.1/index-private.txt
  server.serveStatic("/index-private.txt", LittleFS, "/index.txt").setAuthentication("admin", "admin");

  // ServeStatic static is used to serve static output which never changes over time.
  // This special endpoints automatyically adds caching headers.
  // If a template processor is used, it must enure that the outputed content will always be the ame over time and never changes.
  // Otherwise, do not use serveStatic.
  // Example below: IP never changes.
  // curl -v -X GET http://192.168.4.1/index-static.html
  server.serveStatic("/index-static.html", LittleFS, "/index.html").setTemplateProcessor([](const String& var) -> String {
    if (var == "IP") {
      // for CI, commented out since H2 board doesn ot support WiFi
      // return WiFi.localIP().toString();
      // return WiFi.softAPIP().toString();
      return "127.0.0..1";
    }
    return emptyString;
  });

  // to serve a template with dynamic content (output changes over time), use normal
  // Example below: content changes over tinme do not use serveStatic.
  // curl -v -X GET http://192.168.4.1/index-dynamic.html
  server.on("/index-dynamic.html", HTTP_GET, [](AsyncWebServerRequest* request) {
    request->send(LittleFS, "/index.html", "text/html", false, [](const String& var) -> String {
      if (var == "IP")
        return String(random(0, 1000));
      return emptyString;
    });
  });

  // Issue #14: assert failed: tcp_update_rcv_ann_wnd (needs help to test fix)
  // > curl -v http://192.168.4.1/issue-14
  pinMode(4, OUTPUT);
  server.on("/issue-14", HTTP_GET, [](AsyncWebServerRequest* request) {
    digitalWrite(4, HIGH);
    request->send(LittleFS, "/index.txt", "text/pain");
    delay(500);
    digitalWrite(4, LOW);
  });

  /*
    Chunked encoding test: sends 16k of characters.
    ❯ curl -N -v -X GET -H "origin: http://192.168.4.1" http://192.168.4.1/chunk
  */
  server.on("/chunk", HTTP_HEAD | HTTP_GET, [](AsyncWebServerRequest* request) {
    AsyncWebServerResponse* response = request->beginChunkedResponse("text/html", [](uint8_t* buffer, size_t maxLen, size_t index) -> size_t {
      if (index >= 16384)
        return 0;
      memset(buffer, characters[charactersIndex], maxLen);
      charactersIndex = (charactersIndex + 1) % sizeof(characters);
      return maxLen;
    });
    request->send(response);
  });

  // curl -N -v -X GET http://192.168.4.1/chunked.html --output -
  // curl -N -v -X GET -H "if-none-match: 4272" http://192.168.4.1/chunked.html --output -
  server.on("/chunked.html", HTTP_GET, [](AsyncWebServerRequest* request) {
    String len = String(htmlContentLength);

    if (request->header(asyncsrv::T_INM) == len) {
      request->send(304);
      return;
    }

    AsyncWebServerResponse* response = request->beginChunkedResponse("text/html", [](uint8_t* buffer, size_t maxLen, size_t index) -> size_t {
      Serial.printf("%u / %u\n", index, htmlContentLength);

      // finished ?
      if (htmlContentLength <= index) {
        Serial.println("finished");
        return 0;
      }

      // serve a maximum of 1024 or maxLen bytes of the remaining content
      const int chunkSize = min((size_t)1024, min(maxLen, htmlContentLength - index));
      Serial.printf("sending: %u\n", chunkSize);

      memcpy(buffer, htmlContent + index, chunkSize);

      return chunkSize;
    });

    response->addHeader(asyncsrv::T_Cache_Control, "public,max-age=60");
    response->addHeader(asyncsrv::T_ETag, len);

    request->send(response);
  });

  // time curl -N -v -G -d 'd=3000' -d 'l=10000'  http://192.168.4.1/slow.html --output -
  server.on("/slow.html", HTTP_GET, [](AsyncWebServerRequest* request) {
    uint32_t d = request->getParam("d")->value().toInt();
    uint32_t l = request->getParam("l")->value().toInt();
    Serial.printf("d = %" PRIu32 ", l = %" PRIu32 "\n", d, l);
    AsyncWebServerResponse* response = request->beginChunkedResponse("text/html", [d, l](uint8_t* buffer, size_t maxLen, size_t index) -> size_t {
      Serial.printf("%u\n", index);
      // finished ?
      if (index >= l)
        return 0;

      // slow down the task by 2 seconds
      // to simulate some heavy processing, like SD card reading
      delay(d);

      memset(buffer, characters[charactersIndex], 256);
      charactersIndex = (charactersIndex + 1) % sizeof(characters);
      return 256;
    });

    request->send(response);
  });

  /*
    ❯ 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); // overrides previous one
      response->addHeader(asyncsrv::T_Content_Type, "foo");
      response->setContentType("application/octet-stream"); // overrides previous one
      // ...
      request->send(response);
    } else {
      // ...
    }
  });

  // Send a GET request to <IP>/get?message=<message>
  server.on("/get", HTTP_GET, [](AsyncWebServerRequest* request) {
    String message;
    if (request->hasParam(PARAM_MESSAGE)) {
      message = request->getParam(PARAM_MESSAGE)->value();
    } else {
      message = "No message sent";
    }
    request->send(200, "text/plain", "Hello, GET: " + message);
  });

  // Send a POST request to <IP>/post with a form field message set to <message>
  server.on("/post", HTTP_POST, [](AsyncWebServerRequest* request) {
    String message;
    if (request->hasParam(PARAM_MESSAGE, true)) {
      message = request->getParam(PARAM_MESSAGE, true)->value();
    } else {
      message = "No message sent";
    }
    request->send(200, "text/plain", "Hello, POST: " + message);
  });

#if __has_include("ArduinoJson.h")
  // JSON

  // sends JSON
  // curl -v -X GET http://192.168.4.1/json1
  server.on("/json1", HTTP_GET, [](AsyncWebServerRequest* request) {
    AsyncJsonResponse* response = new AsyncJsonResponse();
    JsonObject root = response->getRoot().to<JsonObject>();
    root["hello"] = "world";
    response->setLength();
    request->send(response);
  });

  // curl -v -X GET http://192.168.4.1/json2
  server.on("/json2", HTTP_GET, [](AsyncWebServerRequest* request) {
    AsyncResponseStream* response = request->beginResponseStream("application/json");
    JsonDocument doc;
    JsonObject root = doc.to<JsonObject>();
    root["foo"] = "bar";
    serializeJson(root, *response);
    request->send(response);
  });

  // curl -v -X POST -H 'Content-Type: application/json' -d '{"name":"You"}' http://192.168.4.1/json2
  // curl -v -X PUT -H 'Content-Type: application/json' -d '{"name":"You"}' http://192.168.4.1/json2
  jsonHandler->setMethod(HTTP_POST | HTTP_PUT);
  jsonHandler->onRequest([](AsyncWebServerRequest* request, JsonVariant& json) {
    serializeJson(json, Serial);
    AsyncJsonResponse* response = new AsyncJsonResponse();
    JsonObject root = response->getRoot().to<JsonObject>();
    root["hello"] = json.as<JsonObject>()["name"];
    response->setLength();
    request->send(response);
  });

  // MessagePack

  // receives MessagePack and sends MessagePack
  msgPackHandler->onRequest([](AsyncWebServerRequest* request, JsonVariant& json) {
    // JsonObject jsonObj = json.as<JsonObject>();
    // ...

    AsyncMessagePackResponse* response = new AsyncMessagePackResponse();
    JsonObject root = response->getRoot().to<JsonObject>();
    root["hello"] = "world";
    response->setLength();
    request->send(response);
  });

  // sends MessagePack
  server.on("/msgpack1", HTTP_GET, [](AsyncWebServerRequest* request) {
    AsyncMessagePackResponse* response = new AsyncMessagePackResponse();
    JsonObject root = response->getRoot().to<JsonObject>();
    root["hello"] = "world";
    response->setLength();
    request->send(response);
  });
#endif

  events.onConnect([](AsyncEventSourceClient* client) {
    if (client->lastId()) {
      Serial.printf("SSE Client reconnected! Last message ID that it gat is: %" PRIu32 "\n", client->lastId());
    }
    client->send("hello!", NULL, millis(), 1000);
  });

  server.on("/sse", HTTP_GET, [](AsyncWebServerRequest* request) {
    request->send(200, "text/html", SSE_HTLM);
  });

  ws.onEvent([](AsyncWebSocket* server, AsyncWebSocketClient* client, AwsEventType type, void* arg, uint8_t* data, size_t len) {
    (void)len;
    if (type == WS_EVT_CONNECT) {
      wsClients++;
      ws.textAll("new client connected");
      Serial.println("ws connect");
      client->setCloseClientOnQueueFull(false);
      client->ping();
    } else if (type == WS_EVT_DISCONNECT) {
      wsClients--;
      ws.textAll("client disconnected");
      Serial.println("ws disconnect");
    } else if (type == WS_EVT_ERROR) {
      Serial.println("ws error");
    } else if (type == WS_EVT_PONG) {
      Serial.println("ws pong");
    } else if (type == WS_EVT_DATA) {
      AwsFrameInfo* info = (AwsFrameInfo*)arg;
      String msg = "";
      if (info->final && info->index == 0 && info->len == len) {
        if (info->opcode == WS_TEXT) {
          data[len] = 0;
          Serial.printf("ws text: %s\n", (char*)data);
        }
      }
    }
  });

  // SSS endpoints
  // sends a message every 10 ms
  //
  // go to http://192.168.4.1/sse
  // > curl -v -N -H "Accept: text/event-stream" http://192.168.4.1/events
  //
  // some perf tests:
  // launch 16 concurrent workers for 30 seconds
  // > for i in {1..10}; do ( count=$(gtimeout 30 curl -s -N -H "Accept: text/event-stream" http://192.168.4.1/events 2>&1 | grep -c "^data:"); echo "Total: $count events, $(echo "$count / 4" | bc -l) events / second" ) & done;
  // > for i in {1..16}; do ( count=$(gtimeout 30 curl -s -N -H "Accept: text/event-stream" http://192.168.4.1/events 2>&1 | grep -c "^data:"); echo "Total: $count events, $(echo "$count / 4" | bc -l) events / second" ) & done;
  //
  // With AsyncTCP, with 16 workers: a lot of "Event message queue overflow: discard message", no crash
  //
  // Total: 1711 events, 427.75 events / second
  // Total: 1711 events, 427.75 events / second
  // Total: 1626 events, 406.50 events / second
  // Total: 1562 events, 390.50 events / second
  // Total: 1706 events, 426.50 events / second
  // Total: 1659 events, 414.75 events / second
  // Total: 1624 events, 406.00 events / second
  // Total: 1706 events, 426.50 events / second
  // Total: 1487 events, 371.75 events / second
  // Total: 1573 events, 393.25 events / second
  // Total: 1569 events, 392.25 events / second
  // Total: 1559 events, 389.75 events / second
  // Total: 1560 events, 390.00 events / second
  // Total: 1562 events, 390.50 events / second
  // Total: 1626 events, 406.50 events / second
  //
  // With AsyncTCP, with 10 workers:
  //
  // Total: 2038 events, 509.50 events / second
  // Total: 2120 events, 530.00 events / second
  // Total: 2119 events, 529.75 events / second
  // Total: 2038 events, 509.50 events / second
  // Total: 2037 events, 509.25 events / second
  // Total: 2119 events, 529.75 events / second
  // Total: 2119 events, 529.75 events / second
  // Total: 2120 events, 530.00 events / second
  // Total: 2038 events, 509.50 events / second
  // Total: 2038 events, 509.50 events / second
  //
  // With AsyncTCPSock, with 16 workers: ESP32 CRASH !!!
  //
  // With AsyncTCPSock, with 10 workers:
  //
  // Total: 1242 events, 310.50 events / second
  // Total: 1242 events, 310.50 events / second
  // Total: 1242 events, 310.50 events / second
  // Total: 1242 events, 310.50 events / second
  // Total: 1181 events, 295.25 events / second
  // Total: 1182 events, 295.50 events / second
  // Total: 1240 events, 310.00 events / second
  // Total: 1181 events, 295.25 events / second
  // Total: 1181 events, 295.25 events / second
  // Total: 1183 events, 295.75 events / second
  //
  server.addHandler(&events);

  // Run in terminal 1: websocat ws://192.168.4.1/ws => stream data
  // Run in terminal 2: websocat ws://192.168.4.1/ws => stream data
  // Run in terminal 3: websocat ws://192.168.4.1/ws => should fail:
  /*
❯  websocat ws://192.168.4.1/ws
websocat: WebSocketError: WebSocketError: Received unexpected status code (503 Service Unavailable)
websocat: error running
  */
  server.addHandler(&ws).addMiddleware([](AsyncWebServerRequest* request, ArMiddlewareNext next) {
    if (ws.count() > 2) {
      // too many clients - answer back immediately and stop processing next middlewares and handler
      request->send(503, "text/plain", "Server is busy");
    } else {
      // process next middleware and at the end the handler
      next();
    }
  });

  // Reset connection on HTTP request:
  // for i in {1..20}; do curl -v -X GET https://192.168.4.1:80; done;
  // The heap size should not decrease over time.

#if __has_include("ArduinoJson.h")
  server.addHandler(jsonHandler);
  server.addHandler(msgPackHandler);
#endif

  server.onNotFound(notFound);

  server.begin();
}

uint32_t lastSSE = 0;
uint32_t deltaSSE = 10;

uint32_t lastWS = 0;
uint32_t deltaWS = 100;

uint32_t lastHeap = 0;

void loop() {
  uint32_t now = millis();
  if (now - lastSSE >= deltaSSE) {
    events.send(String("ping-") + now, "heartbeat", now);
    lastSSE = millis();
  }
  if (now - lastWS >= deltaWS) {
    ws.printfAll("kp%.4f", (10.0 / 3.0));
    // for (auto& client : ws.getClients()) {
    //   client.printf("kp%.4f", (10.0 / 3.0));
    // }
    lastWS = millis();
  }
#ifdef ESP32
  if (now - lastHeap >= 2000) {
    Serial.printf("Free heap: %" PRIu32 "\n", ESP.getFreeHeap());
    lastHeap = now;
  }
#endif
}