Arduino IDE ESP32 all-in-one sketch: WIFI NAT, MQTTs Broker and MQTT client app

This is an ESP32/Arduino sketch to combine some code fragments from other PlatformIO/ESPIDF sources. Background: I wanted to have a combined solution running on a single ESP32 for a control app and found different pieces of code for PlatformIO and ESPIDF which I tried to combine in one Arduino IDE sketch for simplicity. I also wanted a secure MQTT broker in the core to protect WIFI communication and easy configuration and OTA update via web page. The web page is password protected.

ESP32 NAT code inspired by https://github.com/paclema/esp32_lwip_nat_example !Needs either ESP32 Arduino core 2.05 plus liblwip.a and libvfs.a update or an ESP32 Arduino core with NAPT compiled in. For updating NAPT support: (Windows) in C:\Users\xy\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.5\tools\sdk\esp32\lib replace the 2 files. Includes a modified version of a configuration web interface including OTA update support with parameters stored in nvs (erase by holding GPIO23 low at boot).

TinyMqtt broker code modified for use of ESP32_HTTPS_Server library for a simple MQTT broker with TLS. Based on TinyMqtt https://github.com/hsaturn/TinyMqtt and ESP32_HTTPS_Server https://github.com/fhessel/esp32_https_server libraries. Just for my application needs I modified the TinyMqtt code and combined it with slightly adapted HTTPSServer and HTTPSConnection classes as link to the ESP32_HTTPS_Server library to make use of HTTPSConnections instead of WiFiClient on the transport level. Login setting for username and password and check added, default is "" "". QoS, certificate check, retained messages etc. not checked/finished yet!

Plus an example app which for simplicity connects locally to the MQTT broker as subroutine.

Essential function tested: Sketch for WIFI NAT plus simple MQTTS broker allowing communication of several MQTTS clients via e.g. port 8883 with TLS with a local client app.

Note: streaming functions only necessary for debugging placed in extra file MqttStreaming.h