The most popular mobile app for the IOT. Works with anything: ESP8266, Arduino, Raspberry Pi, SparkFun and others.
Blynk is a platform with iOS and Android apps to control Arduino, ESP8266, Raspberry Pi and the likes over the Internet.
You can easily build graphic interfaces for all your projects by simply dragging and dropping widgets
Config file set in /opt/BlynkServer/blynk.conf (need be adapted on your need)
source : https://github.com/blynkkk/blynk-server