This chapter discusses how to use Built-in Topics.
Connext DDS must discover and keep track of remote entities, such as new participants in the DDS domain. This information may also be important to the application itself, which may want to react to this discovery or access it on demand. To support these needs, Connext DDS provides built-in Topics (“DCPSParticipant”, “DCPSPublication”, “DCPSSubscription” in Figure: Built-in Writers and Readers for Discovery ) and the corresponding built-in DataReaders that you can use to access this discovery information.
The discovery information is accessed just as if it is normal application data. This allows the application to know (either via listeners or by polling) when there are any changes in those values. Note that only entities that belong to a different DomainParticipant are being discovered and can be accessed through the built-in readers. Entities that are created within the local DomainParticipant are not included as part of the data that can be accessed by the built-in readers.
Built-in topics contain information about the remote entities, including their QoS policies. These QoS policies appear as normal fields inside the topic’s data, which can be read by means of the built-in Topic. Additional information is provided to identify the entity and facilitate the application logic.
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