MQTT to Command-line Applications Gateway

Create virtual MQTT-controlled command-line gateways for hardware displays. Expose your locally running applications or devices (e.g. monitor input sources via ddcutil) to your home automation server such as Home Assistant.

## Installation

Follow the standard installation instructions to set up the application and configure it to run as a Docker container or directly on your system.

Configuration

This application expects a configuration file named config.yaml, located in:

• $XDG_CONFIG_HOME/mqtt2cmd or $HOME/.config/mqtt2cmd on Linux

Sample Configuration

Below is an example configuration that sets up separate MQTT data points for each monitor input from 0x01 to 0x12. The get_state command is defined once per display (since ddcutil returns the currently active input), and each input has its fixed set_value command:

app-id: "screendaemon"
mqtt:
  broker: "tcp://your-mqtt-server-address:1883"
  username: "mqtt-user"
  password: "your-mqtt-password"

displays:
  - name: "Monitor 1"
    refresh: "1m"
    get_state: "ddcutil getvcp 0x60"
    inputs:
      - name: "VGA-1"
        set_value: "ddcutil setvcp 0x60 0x01"
      - name: "VGA-2"
        set_value: "ddcutil setvcp 0x60 0x02"
      - name: "HDMI-1"
        set_value: "ddcutil setvcp 0x60 0x11"
      - name: "HDMI-2"
        set_value: "ddcutil setvcp 0x60 0x12"

log:
  path: "/workspace/internal/config/logs/screendaemon.log"

How It Works

1. Subscribes to MQTT topics with a prefix based on app-id for each input.
2. Publishes the current input (queried via the shared get_state command) to a topic like screendaemon/displays/Monitor 1.
3. Publishes overall application availability to screendaemon/available and per-display availability to screendaemon/displays/Monitor 1/available.
4. Each input's fixed set_value command is executed when a corresponding MQTT command is received.

Sample Home Assistant Configuration

mqtt:
  switch:
    - name: "Monitor 1 HDMI-1"
      state_topic: "screendaemon/displays/Monitor 1"
      command_topic: "screendaemon/displays/Monitor 1/set"
      payload_on: "0x11"
      availability:
        - topic: "screendaemon/available"
        - topic: "screendaemon/displays/Monitor 1/available"
      availability_mode: "all"

Docker Run Example

docker run --privileged -v /srv/docker/appdata/screendaemon/config:/workspace/internal/config -v /dev:/dev screen-daemon

This command mounts the configuration and device files correctly.

Conclusion

This updated README reflects the new concept: Each display uses a shared get_state command (since ddcutil always returns the active input) and separate, fixed set_value commands for each input—ideal for integration into Home Assistant.