使用 pydbus 库通过会话总线发送信号

Question

我正在使用pydbus，并且我已经成功地使用它来监听会话总线上的信号（在“客户端”）。我现在想编写服务器端，程序在每次触发动作时都会发送一个信号（例如，当它在 FS 上写入文件时）。我真的没有在他们的 GitHub 上得到任何这样的例子。他们只展示了如何编写一个基本的服务器，它有一堆客户端可以调用的方法（但这不是我想要的信号）。

仅供参考，客户端非常简单，看起来像这样：

# Subscribe to DBus dump signal
session_bus = SessionBus()
session_bus.subscribe(iface='my.iface',
                      signal='my_signal_name',
                      object='/my/object',
                      signal_fired=my_callback)

# Create and run main loop
loop = GObject.MainLoop()
loop.run()

其中my_callback 是每次侦听事件弹出时调用的方法（在本例中为my_signal_name）

谢谢帮助。

Answer 1

下面的python3/pydbus程序会每秒发布一个随机整数到会话D-Bus上。

#!/usr/bin/env python3
#!
from pydbus.generic import signal
from pydbus import SessionBus
from gi.repository import GLib
import random
loop = GLib.MainLoop()
interface_name = "org.example.project_1.server_1"
bus = SessionBus()


class Server_XML(object):
    """
    Server_XML definition.
    Emit / Publish a signal that is a random integer every second 
    type='i' for integer. 
    """
    dbus = """
    <node>
        <interface name="org.example.project_1.server_1">
            <signal name="app_1_signal">
                <arg type='i'/>
            </signal>
        </interface>
    </node>
    """
    app_1_signal = signal()

def repeating_timer():
    """Generate random integer between 0 and 100 and emit over Session D-Bus
    return True to keep the GLib timer calling this function once a second."""
    random_integer = random.randint(0,100)
    print(random_integer)
    emit.app_1_signal(random_integer)
    return True


if __name__=="__main__":
    # Setup server to emit signals over the DBus
    emit = Server_XML()
    bus.publish(interface_name, emit)
    # Setup repeating timer
    GLib.timeout_add_seconds(interval=1, function=repeating_timer) 
    # Run loop with graceful ctrl C exiting.
    try:
        loop.run()
    except KeyboardInterrupt as e:
        loop.quit()
        print("\nExit by Control C")

打开另一个 linux 控制台终端并使用 gdbus 实用程序来验证整数是否正在会话总线上发布。比如……

$ gdbus monitor --session --dest org.example.project_1.server_1
Monitoring signals from all objects owned by org.example.project_1.server_1
The name org.example.project_1.server_1 is owned by :1.618
/org/example/project_1/server_1: org.example.project_1.server_1.app_1_signal (36,)
/org/example/project_1/server_1: org.example.project_1.server_1.app_1_signal (37,)
/org/example/project_1/server_1: org.example.project_1.server_1.app_1_signal (25,)

以下python3 / pydbus客户端程序订阅正在会话D-Bus上发布的随机整数...

#!/usr/bin/env python3
#!
from pydbus.generic import signal
from pydbus import SessionBus
from gi.repository import GLib
loop = GLib.MainLoop()
dbus_filter = "/org/example/project_1/server_1"
bus = SessionBus()


def cb_server_signal_emission(*args):
    """
    Callback on emitting signal from server
    """
    print("Message: ", args)
    print("Data: ", str(args[4][0]))

if __name__=="__main__":
    # Subscribe to bus to monitor for server signal emissions
    bus.subscribe(object = dbus_filter, 
                  signal_fired = cb_server_signal_emission)    
    loop.run()

此客户端程序的控制台输出将与此类似...

$ python3 client_pydbus.py
Message:  (':1.621', '/org/example/project_1/server_1', 'org.example.project_1.server_1', 'app_1_signal', (72,))
Data:  72
Message:  (':1.621', '/org/example/project_1/server_1', 'org.example.project_1.server_1', 'app_1_signal', (46,))
Data:  46
Message:  (':1.621', '/org/example/project_1/server_1', 'org.example.project_1.server_1', 'app_1_signal', (47,))
Data:  47

Answer 2

负责信号的类位于generic 模块中。它看起来记录得很好：

Static signal object

You're expected to set it as a class property::

    class A:
        SomethingHappened = signal()

Declared this way, it can be used on class instances
to connect signal observers::

    a = A()
    a.SomethingHappened.connect(func)

and emit the signal::

    a.SomethingHappened()

You may pass any parameters to the emiting function
- they will be forwarded to all subscribed callbacks.

还有一个使用信号的example in the tutorial。注意最后一行和属性SomeProperty。当 setter 中的 python 属性SomeProperty 发生变化时，信号会通过self.PropertiesChanged("net.lew21.pydbus.TutorialExample", {"SomeProperty": self.SomeProperty}, []) 发出。

from pydbus.generic import signal

class Example(object):
  """
    <node>
      <interface name='net.lew21.pydbus.TutorialExample'>
        <method name='EchoString'>
          <arg type='s' name='a' direction='in'/>
          <arg type='s' name='response' direction='out'/>
        </method>
        <property name="SomeProperty" type="s" access="readwrite">
          <annotation name="org.freedesktop.DBus.Property.EmitsChangedSignal" value="true"/>
        </property>
      </interface>
    </node>
  """

  def EchoString(self, s):
    """returns whatever is passed to it"""
    return s

  def __init__(self):
    self._someProperty = "initial value"

  @property
  def SomeProperty(self):
    return self._someProperty

  @SomeProperty.setter
  def SomeProperty(self, value):
    self._someProperty = value
    self.PropertiesChanged("net.lew21.pydbus.TutorialExample", {"SomeProperty": self.SomeProperty}, [])

  PropertiesChanged = signal()

还有一个notification_server example 使用信号（但不调用）。