mqtt-status

Congratulations! If you are here, you are most likely looking for a quick and simple solution for the issue I also had: a barebones MQTT client sending messages when your computer is on. Well, this does just that. Literally - just that.

Setup

The following is my setup on Linux. Windows should work too, but I haven't checked it, and the solution suddenly stops being simple since there are no instructions anymore. This setup will run a user-level service - running an MQTT client as root written by an internet rando is a VERY stupid idea. I don't judge, but again, you have to figure that out on your own.

Prerequisites: JDK 21 installed.

1. git clone
2. ./gradlew jar
3. Copy build/libs/* to ~/.local/bin/
4. Alternatively - you can download the latest release from here.
5. Create ~/.config/systemd/user and write mqtt_status.service:

   [Unit]
   Description = Very simple MQTT client that updates power status every 30 seconds
   
   [Service]
   ExecStart = /usr/bin/java -jar %h/.local/bin/mqtt-status-1.0.jar
   
   [Install]
   WantedBy = plasma-workspace.target
   

   Your mileage may vary when it comes to WantedBy - check available targets with systemctl --user list-units --type=target.
6. Create ~/.mqttstatus/config.yml:

   mqttHost: localhost
   mqttPort: 1883
   topic: pc/is_powered_on
   onValue: "true"
   offValue: "false"
   retainWill: true
   qos: AT_LEAST_ONCE # available values: AT_MOST_ONCE (0), AT_LEAST_ONCE (1), EXACTLY_ONCE (2)
   interval: 30s

   These are the defaults - in an unlikely scenario you like them all you can skip this step. If not, modify to your liking. You can leave only the properties you want to change.
7. systemctl --user enable mqtt_status.service

Pull requests and improvement ideas are welcome, although new features (and especially more data!) are unlikely to be merged. This solution aims to be extremely simple.