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Integration / D Bus Interview Questions

How does D-Bus introspection work in practice?

In practice, introspection is a plain method call like any other: a client sends a method call to Introspect() on the org.freedesktop.DBus.Introspectable interface, targeting the object path it wants to learn about, and the service replies with an XML string describing that object.

<node>
  <interface name="org.freedesktop.NetworkManager.Device">
    <method name="Disconnect"/>
    <property name="State" type="u" access="read"/>
    <signal name="StateChanged">
      <arg name="new_state" type="u"/>
    </signal>
  </interface>
</node>

The XML also lists any child object paths nested beneath the queried one, which is how tools like D-Feet let you browse an entire service's object tree interactively: introspect the root, follow a child node listed in the response, introspect that, and repeat.

Because this reply is generated dynamically by the service rather than hand-maintained documentation, it always reflects exactly what that running version of the service actually supports.

The Introspect() reply is returned as:
Tools like D-Feet use introspection to:

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