Revision history [back]

You are correct in both your points:

  • the sessionless signal is cached for the duration of the TTL by the router on the emitting side, and
  • the discovery by the signal receiver uses the underlying mDNS mechanism to locate emitters.

The receiver only fetches sessionless signals from those emitters who are advertising that they are emitting a sessionless signal from an interface the receiver is interested in. For About, the receiver is interested in sessionless signals from the org.alljoyn.About interface, and the emitter advertises that it is emitting a sessionless signal from the org.alljoyn.About interface, so the receiver will fetch the signals from the emitter.

In regards to the replacement rule:

The key used on the router to cache the sessionless signal is (sender, object path, interface, member). Sender is your application, object path is the object emitting the signal in your application, and interface and member are the name of the interface and signal that is being emitted.

So any signal emitted by your app with the same key above will replace the cached signal in the router.