Working with D-Bus in Linux's systemd.

Quoting “D-Bus integration in Emacs” ¹, D-Bus is defined as followed

D-Bus is an inter-process communication mechanism for applications residing on the same host. The communication is based on messages. Data in the messages is carried in a structured way, it is not just a byte stream.

According to ¹, name of client application is “a series of identifiers separated by dots”, but an application can install multiple objects under its name which are represents as path like syntax – separated by /. Communications to these applications are either “methods” (requests/responds) or “signals” (pub/sub). These form of communication is called “interface” of the application. Name of Interfaces is append to application’s name.

To be honest, I still don’t know what is the different between object and application. According to ¹, I see “object” (represented as path) as a way to create arbitrary name to refers to a specific application. ²

Say I want to add new client D-Bus application to add org-clock notification functionality in Emacs, I have to put add systemd service file at /usr/share/dbus-1/services/. Note that I am using Ubuntu distro on Wsl2 on Window 10. Example of the file name is org.freedesktop.Notifications.service. I speculate that the file is an “interface” to application named org.freedesktop.Notifications

In org.freedesktop.Notifications.service, I wrote

[D-BUS Service]
Name=org.freedesktop.Notifications
Exec=/usr/lib/notification-daemon/notification-daemon

That’s it.

Peace.

~milfex-lostex

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