write DBUS Services (II)

For the system bus server you would need only to modify line 13 from the sessionbus server and line 7 from the client scripts; to replace SessionBus() with SystemBus(). Let’s also change
the names for the methods and for the service.

The final code would look like this:

#!/usr/bin/env python3

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

from dbus.mainloop.glib import DBusGMainLoop

class Session_DBus(dbus.service.Object):
def __init__(self):
bus_name=dbus.service.BusName('org.me.test_system',bus=dbus.SystemBus())
dbus.service.Object.__init__(self,bus_name,'/org/me/test_system')

@dbus.service.method('org.me.test1')
def session_bus_message1(sefl):
return "Session Bus 1"

@dbus.service.method('org.me.test2')
def session_bus_message2(self):
return "Session Bus 2"

@dbus.service.method('org.me.test2')
def session_bus_strings(self,string1,string2):
return string1+" "+string2

DBusGMainLoop(set_as_default=True)
dbus_service=Session_DBus()

try:
GLib.MainLoop().run()
except KeyboardInterrupt:
print("\nThe MainLoop will close...")
GLib.MainLoop().quit()


And for the clients it would look something like this:
Vers1
#!/usr/bin/env python3

import dbus
bus = dbus.SystemBus()
session = bus.get_object("org.me.test_system", "/org/me/test_system")

method_message1 = session.get_dbus_method('session_bus_message1', 'org.me.test1')
method_message2 = session.get_dbus_method('session_bus_message2', 'org.me.test2')
method_message3 = session.get_dbus_method('session_bus_strings', 'org.me.test2')

print(method_message1())
#interface1 = dbus.Interface(session, "org.me.test1")
#print(interface1.session_bus_message1())
print(method_message2())
print(method_message3("Hello", "World"))Vers2:

#!/usr/bin/env python3

import dbus
bus = dbus.SystemBus()
session = bus.get_object("org.me.test_system", "/org/me/test_system")
interface1 = dbus.Interface(session, "org.me.test1")
interface2 = dbus.Interface(session, "org.me.test2")

print(interface1.session_bus_message1())
print(interface2.session_bus_message2())
print(interface2.session_bus_strings("hello", "world"))

Of course, if you try the same thing now: run the server and then test the clients you would see that you get an error after trying to
turn on the server: a message saying that a specific connection is not allowed to own a service. This thing is because (remember from the first lines of the post) you try (as a regular user) to run a D-Bus that may change the entire system state.

To run the server and test the clients you could to the following:

Create a file in /etc/dbus-1/system.d/ with the name org.me.test_system.conf with the following content:

<!DOCTYPE busconfig PUBLIC
"-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
"http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">

<busconfig>
<!-- Owned only by the root -->
<policy user="root">
<allow own="*"/>
</policy>

<!-- What to allow for users -->
<policy context="default">
<allow send_destination="*"/>
<allow send_interface="*"/>
</policy>

Run the server and then you can test the clients :).
Also if you want to only to run the clients (the server to automatically kick in) you can create a file in
/usr/share/dbus-1/system-services/ with the name org.me.test_system.service that would contain the following lines:

That is all for now and I hope you found this tutorial helping :D.

“In vain have you acquired knowledge if you have not imparted it to others.”
Deuteronomy Rabbah

Have a great day,

George

https://georgemuraruc.wordpress.com/2015/07/16/d-bus-tutorial-for-python/