Entities

The protocol under eProsima Micro XRCE-DDS (XRCE), defines entities that have a direct correspondence with their analogous actors on eProsima Fast RTPS (DDS). The entities manage the communication between eProsima Micro XRCE-DDS Client and the DDS Global Data Space. Entities are stored in the eProsima Micro XRCE-DDS Agent and the eProsima Micro XRCE-DDS Client can create, use and destroy these entities.

The entities are uniquely identified by an ID called Object ID. The Object ID is the way a Client refers to them inside an Agent. In most of the Client request operations is necessary to specify an ID referring to one of the Client entities stored in the Agent.

Type of Entities

These are the entities that the Client can interact with.

Participants
Participants can hold any number of Publishers and/or Subscribers
Publisher
Publishers can hold any number of data writers.
Subscriber
Subscribers can hold any number of data readers.
Topic
Topic data is the base of the communication. A Topic is composed of a name and a data type.
DataWriter
This is the endpoint able to write Topic data.
DataReader
This is the endpoint able to read Topic data.

This figure shows the entities hierarchy

_images/entities_hierarchy.svg