ESP32 Forum

for what is this for?

esp_err_t event_handler(void* ctx, system_event_t* event)
{
return ESP_OK;
}

Event handler is used to tie events from WiFi/Ethernet/LwIP stacks into application logic.

You can see some of the examples in ESP-IDF using these events:
https://github.com/espressif/esp-idf/bl ... .c#L54-L73

For description of events from WiFi driver, please refer to the documentation:
http://esp-idf.readthedocs.io/en/latest ... escription

Documentation about Ethernet/LwIP events is coming up, please check the examples for now.