Node-red und Mosquitto für MQTT auf den Raspberry Pi installieren:
https://www.youtube.com/watch?v=heyH0hgENF8

WiFi - Relais mit Node-red über MQTT schalten:
https://www.youtube.com/watch?v=aHiAVTuKL7M

Node-Red installieren:
<code>
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install build-essential curl npm
bash <(curl -sL https://raw.githubusercontent.com/node-red/linux-installers/master/deb/update-nodejs-and-nodered)
</code>

Dasboard installieren:
<code>
node-red-stop
cd ~/.node-red
npm install node-red-dashboard
</code>


Mosquito installieren:
<code>
sudo apt install mosquitto mosquitto-clients
sudo systemctl enable mosquitto
sudo systemctl status mosquitto
</code>

Mosquito testen:
<code>
Subscribe im Terminal 1
mosquitto_sub -h localhost -t "test/message"
Publish im Terminal 2
mosquitto_pub -h localhost -t "test/message" -m "Hello, world"
</code>

Node-red starten:
<code>
node-red-start
<code>

Code für ESP
https://github.com/Edistechlab/Relais-per-MQTT-schalten/blob/master/MQTT_Output.ino