How to re-initialize ESPAsyncWebServer

Using Arduino Networking, Protocols, and Devices
1

In my application the user can turn off and on the WiFi and, as consequence, the ESPAsyncWebServer. Here my relevant code:

AsyncWebServer _server;

void WebApp::Begin()
{
  MDNS.begin(APP_NAME);
  MDNS.addService("http", "tcp", 80);

  _server.on("/api/datetime", HTTP_GET, [this](AsyncWebServerRequest *request)
  {    
  // do something
  }

  // several other callbacks

  // enable captive portal only if we are in hotspot
  if (_network.Mode() == Network::Modes::Hotspot) _server.addHandler(new CaptiveRequestHandler()).setFilter(ON_AP_FILTER);

  DefaultHeaders::Instance().addHeader("Cache-Control", "no-cache, no-store, must-revalidate");
  DefaultHeaders::Instance().addHeader("Pragma", "no-cache");
  DefaultHeaders::Instance().addHeader("Expires", "0");

  _server.begin();
}

void WebApp::End()
{
  _server.end();
  _isRunning = false;
}

I call these functions here:

// in my main loop if station is enabled
if (WiFi.isConnected())
{
  Serial.print(F("[NET] Connected to: "));
  Serial.println(WiFi.SSID());
  Serial.print(F("[NET] Local IP: "));
  Serial.println(WiFi.localIP());
  Serial.print(F("[NET] RSSI: "));
  Serial.print(WiFi.RSSI());
  Serial.println(" dBm");
  _provisioning.SetNtp();

  webapp.Begin();
  _mode = Modes::Station;
}

or when set the hotspot mode:

Network::setHotspot()
{
    turnOffWifi();
    _mode = _lastMode = Modes::Hotspot;
    IPAddress local_ip(192, 168, 4, 1); 
    IPAddress gateway(192, 168, 4, 1); 
    IPAddress subnet(255, 255, 255, 0);

    WiFi.mode(WIFI_MODE_AP);
    WiFi.softAP(ssid, password);
    WiFi.softAPConfig(local_ip, gateway, subnet);
    WiFi.softAPsetHostname(APP_NAME);
    esp_wifi_set_ps(WIFI_PS_NONE);
    Serial.printf("[NET] Start DNS: %s\n",_dns.start(53, "*", WiFi.softAPIP()) ? "success" : "failed");

    Serial.print(ssid);
    Serial.print(F(" "));
    Serial.println(password);
    Serial.print(F("[NET] Local IP: "));
    Serial.println(WiFi.softAPIP());
    webapp.Begin();
}

void Network::turnOffWifi()
{
    Serial.println("[NET] Turning off Wifi");
    if (webapp.IsRunning()) webapp.End();
    if (sntp_enabled) sntp_stop();
    WiFi.mode(WIFI_OFF);
    while (static_cast<int8_t>(WiFi.status()) > WL_IDLE_STATUS)
    {
        Serial.println(WiFi.status());
        yield();
        delay(500);
    }
    Serial.println("[NET] Done");
}

After 1-2 turn off/on cycle, the ESPAsyncWebServer and DNS services do not start anymore:

[258253][E][AsyncTCP.cpp:1487] begin(): bind error: -8

I found this issue and it seems to be no solution other than to avoid calling the end() function. But in my application I do need to stop the webserver when I switch among WiFi modes (offline/station/hotspot) and when I start a different webserver for provisioning.

Is there a reliable way to stop and restart ESPAsyncWebServer?