You can access the wiring diagram, additional documentation, and code downloads used in this video at https://www.patreon.com/posts/17921563
It's quite a long video, and depending on what hardware you're using not all of it might be relevant to you, so here's a guide to jump to the relevant bits!
00:00 - 05:55 Introduction and Demonstration
05:56 - 07:34 Android client demonstration
07:35 - 13:03 Arduino, Wemos, and Raspberry Pi Wiring
13:04 - 20:01 Installing and testing the Mosquitto MQTT server
20:02 - 37:24 Code for Arduino Ethernet and MQTT client
37:25 - 43:05 Code for Wemos WiFi and MQTT client
43:06 - 48:33 Code for Raspberry Pi MQTT client
48:34 - 50:10 Android client (MQTT Dash)
50:11 - 51:12 Wrapup
As ever, please ask any questions or comments below!