Reference implementation of D-Bus message bus is dbus-daemon.

Monitoring daemon

Message bus provides a set on standard interaces which can be introspected with:

$ dbus-daemon --introspect

To query these interfaces, use dbus-send.

To see who's on the system bus:

$ dbus-send --system \
            --print-reply \
            --type=method_call \
            --dest=org.freedesktop.DBus / org.freedesktop.DBus.ListNames

Get some runtime stats from the daemon:

$ dbus-send --session \
            --dest=org.freedesktop.DBus \
            --type=method_call \
            --print-reply \
            /org/freedesktop/DBus org.freedesktop.DBus.Debug.Stats.GetStats