The Low Level InterfaceΒΆ
The low-level interface allows you to work with messages directly through the MessageBus
with the Message
class. This might be useful in the following cases:
Implementing an application that works with DBus directly like
dbus-send(1)
ordbus-monitor(1)
.Creating a new implementation of the
BaseMessageBus
.Creating clients or services that use an alternative to the standard DBus interfaces.
The primary methods and classes of the low-level interface are:
Mixed use of the low and high level interfaces on the same bus connection is not recommended.
- example:
Call a standard interface
bus = await MessageBus().connect()
msg = Message(destination='org.freedesktop.DBus',
path='/org/freedesktop/DBus',
interface='org.freedesktop.DBus',
member='ListNames',
serial=bus.next_serial())
reply = await bus.call(msg)
assert reply.message_type == MessageType.METHOD_RETURN
print(reply.body[0])
- example:
A custom method handler. Note that to receive these messages, you must add a match rule for the types of messages you want to receive.
bus = await MessageBus().connect()
reply = await bus.call(
Message(destination='org.freedesktop.DBus',
path='/org/freedesktop/DBus',
member='AddMatch',
signature='s',
body=["member='MyMember', interface='com.test.interface'"]))
assert reply.message_type == MessageType.METHOD_RETURN
def message_handler(msg):
if msg.interface == 'com.test.interface' and msg.member == 'MyMember':
return Message.new_method_return(msg, 's', ['got it'])
bus.add_message_handler(message_handler)
await bus.wait_for_disconnect()
- example:
Emit a signal
bus = await MessageBus().connect()
await bus.send(Message.new_signal('/com/test/path',
'com.test.interface',
'SomeSignal',
's', ['a signal']))
- example:
Send a file descriptor. The message format will be the same when received on the client side. You are responsible for closing any file descriptor that is sent or received by the bus. You must set the
negotiate_unix_fd
flag toTrue
in theMessageBus
constructor to use unix file descriptors.
bus = await MessageBus().connect(negotiate_unix_fd=True)
fd = os.open('/dev/null', os.O_RDONLY)
msg = Message(destination='org.test.destination',
path='/org/test/destination',
interface='org.test.interface',
member='TestMember',
signature='h',
body=[0],
unix_fds=[fd])
await bus.send(msg)