dbus Tips

System Bus

/etc/dbus-1/system.d/com.example.calculator.conf

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-Bus Bus Configuration 1.0//EN"
 "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>
  <policy user="<username>">
    <allow own="com.example.calculator" />
    <allow send_destination="com.example.calculator" send_interface="org.freedesktop.DBus.Introspectable" send_member="Introspect" />
    <allow send_destination="com.example.calculator" send_interface="com.example.calculator_interface" send_member="Add" />
  </policy>
</busconfig>

calculator.py

import dbus
import dbus.service
import dbus.mainloop.glib
from gi.repository import GLib

mainloop = None

class Calculator(dbus.service.Object):
    def __init__(self,bus):
        self.path = "/com/example/calculator"
        super().__init__(bus,self.path)
    @dbus.service.method("com.example.calculator_interface",in_signature="ii",out_signature="i")
    def Add(self,a1,a2):
        sum = a1+a2
        print(a1," + ",a2," = ",sum)
        return sum


dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)
bus = dbus.SystemBus()

name = dbus.service.BusName("com.example.calculator",bus)

calc = Calculator(bus)
mainloop = GLib.MainLoop()
print("waiting for some calculations to do...")
try:
    mainloop.run()
except KeyboardInterrupt:
    pass

# システムバスに登録されてるか確認
$ busctl tree --system | grep example
Service com.example.calculator:
  └─ /com/example
    └─ /com/example/calculator
# インターフェースやメソッド等を表示
$ busctl introspect --system com.example.calculator /com/example/calculator
NAME                                TYPE      SIGNATURE RESULT/VALUE FLAGS
com.example.calculator_interface    interface -         -            -
.Add                                method    ii        i            -
org.freedesktop.DBus.Introspectable interface -         -            -
.Introspect                         method    -         s            -
# Addメソッドを実行
$ dbus-send --print-reply --system --type=method_call  --dest=com.example.calculator   /com/
example/calculator   com.example.calculator_interface.Add   int32:1 int32:2