ESP is Crashing/rebooting when using Webserver.h library

[intoku]

Description of the problem

For my application i need to run Webserver.h on port 80 on the ESP32. The program is compiling properly - until "server.begin();" is called - afterwards the program compiles - but crashes when uploaded to ESP.
Have tested the identical code with the standard library WiFi.h, where it works properly.
I have tried with including and not including the Webserver.h - mostly same issue. Furthermore, disabling or fully removing the client.enableHTTPWebUpdater(); did not help,

Is there a way to use the Webserver.h from my script without this conflicts/errors with the EspMQTTClient library?

Other tries:

• When using this script only with WifiClient.h or WiFi.h, and - it works good
• When the EspMQTTClient is included, but i use WiFi.begin(LOCAL_SSID, LOCAL_PASS); inside the setup() - it also works good
• When the EspMQTTClient is included, but i use EspMQTTClient client() - compiles but does not work
• when server.begin() is enabled - the whole application crashes and reboots

Versions

• ESPMQTTClient lib: -1.13.3
• PubSubClient lib: -put version number here-
• Arduino ESP32 / ESP8622 core: ESP32-s2-rc4

Hardware

• Board type : ESP32 or ESP8266 ?
• Board model :ESP32-s2-rc4

Logs

Rebooting...
ESP-ROM:esp32s2-rc4-20191025
Build:Oct 25 2019
rst:0x3 (RTC_SW_SYS_RST),boot:0x8 (SPI_FAST_FLASH_BOOT)
Saved PC:0x40026d81
SPIWP:0xee
mode:DIO, clock div:1
load:0x3ffe6100,len:0x524
load:0x4004c000,len:0xa70
load:0x40050000,len:0x292c
entry 0x4004c18c

assert failed: tcpip_send_msg_wait_sem IDF/components/lwip/lwip/src/api/tcpip.c:455 (Invalid mbox)

Backtrace:0x4002735a:0x3ffd31000x4002c881:0x3ffd3120 0x40031c75:0x3ffd3140 0x400a9ea9:0x3ffd3270 0x400b8da5:0x3ffd32a0 0x400b8df6:0x3ffd32c0 0x400a9721:0x3ffd3310 0x4008bd12:0x3ffd3330 0x4008bd8c:0x3ffd3380 0x4008f469:0x3ffd33a0 0x40083593:0x3ffd33c0 0x40093332:0x3ffd3420 

ELF file SHA256: 0000000000000000

C++ code

#include "EspMQTTClient.h"
//#include <WiFiClient.h>
#include <Wire.h>
#include <WebServer.h>
#define LOCAL_SSID "************"
#define LOCAL_PASS "************"

WebServer server(80);

  EspMQTTClient client(
    LOCAL_SSID, LOCAL_PASS, 
    "***********",  // MQTT Broker server ip
    "**********",   // Can be omitted if not needed
    "**********",   // Can be omitted if not needed
    "random_name",     // Client name that uniquely identify your device
    1883              // The MQTT port, default to 1883. this line can be omitted
  );

void setup(){
  //WiFi.begin(LOCAL_SSID, LOCAL_PASS);
  //while (WiFi.status() != WL_CONNECTED) { delay(500); }
  Serial.begin(115200);
  client.enableDebuggingMessages();
  
  server.on("/get", ShowGET);
  // server.begin();

  Serial.print("IP address: "); Serial.println(WiFi.localIP());
}

void onConnectionEstablished() {
    client.subscribe("WAVE/500/status/#", [](const String & topic, const String & payload) {
      String new_payload=payload;
    });
}

void loop()
{
  client.loop();
  server.handleClient();
}

void ShowGET() {
  Serial.println("works");
  server.send(200, "text/plain", "");
}

[intoku]

Accidentally have found that if "server.begin();" is placed inside the "onConnectionEstablished()" function - than the server works. Not sure if this is the correct way to do it - can be helpful to anyone that needs the webserver active

[github-ccnt-nib]

Hey folks. Ran into the same issue. Wanted to run my own webserver alongside the built-in http-update server without success, getting the boot-loop as shown above.
I solved the issue by exposing the webserver which is already built into the esp32mqttclient class.
Inside EspMQTTClient.h add:
WebServer* webserver();
under the public: section (e.g. under enableHTTPWebUpdater())
Inside EspMQTTClient.cpp add:
WebServer* EspMQTTClient::webserver() { return _httpServer; }

Then you can move the http-update url to some path, eg.
client.enableHTTPWebUpdater("/update");
and add all hooks, you want for your own webserver like so:
client.webserver()->on("/", handle_root);
the handle_root function needs to look like:
void handle_root() { client.webserver()->send(200, "text/plain", "your answer"); }