MDNS fails on esp32 because called before network is established

[jbaudoux]

Describe the bug

MDNS is started before network is established causing failure. Device is not crashing, just MDNS fails

[   190][E][ESPmDNS.cpp:65] begin(): Failed starting MDNS
Error setting up MDNS responder

Better use event handler:

void onNetworkConnected() {
  MDNS.begin("milight-hub");
}
#if defined(ESP8266)
void onWifiConnect(const WiFiEventStationModeGotIP& event) {
  onNetworkConnected()
} 
#elif defined(ESP32)
void onEvent(arduino_event_id_t event) {
  switch (event) {
    case SYSTEM_EVENT_STA_GOT_IP:
    case ARDUINO_EVENT_ETH_GOT_IP:
      onNetworkConnected();
      break;
    default: break;
  }
}
#endif

Steps to reproduce

Start device

Expected behavior

MDNS should succeed

Setup information

Firmware version

1.13.1

Output of http://milight-hub.local/about

{"firmware":"milight-hub","version":"1.13.1-beta2","ip_address":"172.19.3.37","reset_reason":"7","variant":"esp32","free_heap":215768,"arduino_version":"v4.4.6-dirty","free_stack":5548,"flash_used":2259,"flash_total":113201,"flash_pct_free":98,"mqtt":{"configured":true,"connected":true,"status":"Connected"},"queue_stats":{"length":0,"dropped_packets":0}}

Output of http://milight-hub.local/settings

{"admin_username":"","admin_password":"","ce_pin":4,"csn_pin":5,"reset_pin":0,"led_pin":-2,"radio_interface_type":"nRF24","packet_repeats":50,"http_repeat_factor":1,"auto_restart_period":0,"mqtt_server":"172.19.3.140","mqtt_username":"","mqtt_password":"","mqtt_topic_pattern":"milight/commands/:device_id/:device_type/:group_id","mqtt_update_topic_pattern":"","mqtt_state_topic_pattern":"milight/state/:device_id/:device_type/:group_id","mqtt_client_status_topic":"milight/client_status","simple_mqtt_client_status":true,"discovery_port":48899,"listen_repeats":3,"state_flush_interval":10000,"mqtt_state_rate_limit":500,"mqtt_debounce_delay":500,"mqtt_retain":true,"packet_repeat_throttle_sensitivity":0,"packet_repeat_throttle_threshold":200,"packet_repeat_minimum":3,"enable_automatic_mode_switching":false,"led_mode_wifi_config":"Fast toggle","led_mode_wifi_failed":"On","led_mode_operating":"Slow blip","led_mode_packet":"Flicker","led_mode_packet_count":3,"hostname":"milight-hub","rf24_power_level":"MAX","rf24_listen_channel":"LOW","wifi_static_ip":"","wifi_static_ip_gateway":"","wifi_static_ip_netmask":"","packet_repeats_per_loop":10,"home_assistant_discovery_prefix":"homeassistant/","wifi_mode":"g","default_transition_period":500,"rf24_channels":["LOW","MID","HIGH"],"device_ids":[],"gateway_configs":[],"group_state_fields":["state","brightness","computed_color","mode","color_temp","color_mode"],"ignored_listen_protocols":[]}

Additional context

Board: esp32dev
Build with pio run --target upload -e esp32