MQTT to D-Bus Notifications

This is a small program which can subscribe to one ore more MQTT topics and publish them as desktop notifications via D-Bus. The program is intended to run in the background of a desktop session and generate desktop notifications from MQTT messages.

Requirements

• A running MQTT message broker (e.g. Mosquitto).
• A Linux desktop environment which supports notifications and which publishes a D-Bus interface for creating notifications

Installation

The only option right no is to install from source. First, Install Go.

Next, Install Go dependencies:

• Go bindings for D-Bus
• Go MQTT client

$ go get github.com/godbus/dbus
$ go get github.com/eclipse/paho.mqtt.golang

Next, install the mqtt-dbus-notify app:

$ go install github.com/akeil/mqtt-dbus-notify

Configuration

The configuration file is expected at $HOME/.config/mqtt-dbus-notify.json. A sample configuration looks like this:

{
    "host": "localhost",
    "port": 1883,
    "username": "",
    "password": "",
    "secure": false,
    "timeout": 5,
    "icon": "dialog-information",
    "subscriptions": [
        {
            "topic": "calendar/alert",
            "icon": "appointment-soon",
            "title": "Appointment",
            "body": "{{.}}"
        },
        {
            "topic": "test/notify",
        }
    ]
}

Aside from the subscriptions, these are also the default values. If the MQTT broker is running on the same computer on the default port (1883) and without authentication, no configuration is required.

The secure option uses a TLS encrypted connection, usually over port 8883.

Subscriptions

To generate notifications, one or more Subscriptions need to be configured. A subscription must at least specify one topic . Topic wildcards can be used.

A subscription can also specify a custom icon. If none is specified, the default icon will be used (see below).

By default, the body of the MQTT message is used as the title for the notification. If the message consists of multiple lines, the first line is used as the title and the remaining lines as the body.

Templates for Title and Body

A subscription can have a customized title and body. These are Go templates. Use {{.}} to refer to the MQTT message payload.

Within the title and body template, the Topic function can be used to return a part of the MQTT topic. For example:

    ...
    "topic": "weather/berlin/temperature"
    "title": "{{.Topic 2}} in {{.Topic 1}}"
    ...

This will display "temperature in berlin" as the notification title.

Icons

Icons can be specified using standard icon names like "appointment-soon". Look at the directory structure below /usr/share/icons/ to see which icons are available.

Alternatively, the absolute path to an image file can be used as an icon. like this:

{
    "topic": "my/topic",
    "icon": "/home/yourname/myicon.png"
}

Running

The program needs to run within the context of a desktop session. Otherwise, it would not be able to publish notifications.

A simple way to do this is to create a mqtt-dbus-notify.desktop file and place it in $HOME/.config/autostart.

[Desktop Entry]
Name=MQTT-DBus-Notify
Comment=Desktop notifications from MQTT messages
NoDisplay=false
Exec=$GOHOME/bin/mqtt-dbus-notify
Type=Application
Categories=Accessoires;

Most (all?) Desktop Environments should support this and run the command listed under Exec when you log into the DE.