Below is a list of the  articles to follow  to build your IOT environment consisting of sensors and relays with Beaglebone, ESP8266 and MQTT Mosquitto server.

1. Architecture and Mqtt protocol
2. Mosquitto Mqtt installation on Beaglebone
3. Mqtt on ESP8266
4. Temperature sensor on ESP8266 with Mqtt protocol
5. Relay on ESP8266 with Mqtt protocol
6. Configuration of Http server, Mqtt websocket protocol on Beaglebone
7. Freeboard dashboard installation and configuration on Beaglebone
8. Android client to manage sensors with Mqtt protocol