title: dbus signal handler for e NetworkManager VPN connection
body: <p>I need to develop some python code to be executed when a VPN connection is established, the VPN is controlled from NetworkManager, I am trying to figure how to use an NM DBUS event for this.</p>
  
  <p>Using "dbus-monitor --system" I was able to identify the connect signal:</p>
  
  <pre><code>signal sender=:1.1 -&gt; dest=(null destination) serial=464 path=/org/freedesktop/NetworkManager/ActiveConnection/3; interface=org.freedesktop.NetworkManager.VPN.Connection; member=PropertiesChanged
     array [
        dict entry(
           string "VpnState"
           variant             uint32 5
        )
        dict entry(
           string "State"
           variant             uint32 2
        )
     ]
  </code></pre>
  
  <p>Now I need to identify the corresponding signal handler calling signature:</p>
  
  <pre><code>bus.add_signal_receiver(
     handler_name_in_your_program,
     "signal_name",
     "interface_name",
     "connection_name",
     "object_name"
  </code></pre>
  
  <p>)</p>
  
  <p>Can someone help me translating the dbus-monitor trace output into the corresponding function values for the bus sginal handler ?</p>