How to use UserDataQos on EDP layer

[advancenXX]

We could add UserData to DomainParticipantQos when create_participant(), and receive it on_participant_discovery().
We could also add UserData to DataWriterQos when create_datawriter(), but how could we receive it?

[JLBuenoLopez]

Hi @advancenXX

DomainParticipantListener class implements also the on_subscriber_discovery and on_publisher_discovery callbacks. I know that these names might be misleading because DDS specification uses the terms Subscriber and Publisher as the factories for the DataWriter and DataReader endpoints. These names are legacy from the old FastRTPS API (non-DDS compliant). These callbacks are called when a DDS DataWriter or DDS DataReader is discovered (and not when a DDS Publisher/Subscriber is). You might access the UserData QoS information in a similar way as in the on_participant_discovery callback.

I hope this information answers your question.

[advancenXX]

Thanks, I find on_publisher_discovery too and that is what I want.

[advancenXX]

@JLBuenoLopez-eProsima hello, I add a on_publisher_discovery participant listener simply to HelloWorldExample, both for Publisher and Subscriber side, like,
DomainParticipantFactory::get_instance()->create_participant(0, pqos, &part_listener_);
Then, listener works correctly, but Subscriber could never receive data.
What could I do to fix this problem?

[EduPonz]

Hi @advancenXX,

This is because the default value for the StatusMask on participant creation is all, meaning the participant listener will capture all the callbacks coming from all its contained entities. Since your participant listener is not overriding the on_data_on_readers function, the default implementation it's being used, which is empty. You can read more about it here.

The easiest fix is to set the StatusMask to none when creating your participant, as the on_participant|publisher|subscriber_discovery callback are not affected by it.

[advancenXX]

Thanks, I will try it on my device.