.. index:: DomainParticipants

.. _domainparticipants_bm:

==================
DomainParticipants
==================

A Domain is a specific subsection of the DDS shared-dataspace and identified by its 
domain ID, which is a 32-bit unsigned integer.

Data exchanges are limited to the domain they are made on. For example, data exchanged 
on domain 2 is not visible on domain 8.

To exchange data you must create a DomainParticipant, which is an entrypoint for the 
program on the shared dataspace's domain.

To specify the default domain ID:

.. tabs::

    .. group-tab:: Core DDS (C)

		.. code:: C
			
			dds_entity_t participant = dds_create_participant (DDS_DOMAIN_DEFAULT, NULL, NULL);

    .. group-tab:: C++

		.. code:: C++
			
			dds::domain::DomainParticipant participant(domain::default_id());

    .. group-tab:: Python

		.. code:: Python

			dp = DomainParticipant()

To specify with domain ID 5:

.. tabs::

    .. group-tab:: Core DDS (C)

		.. code:: C
			
			dds_entity_t participant = dds_create_participant (5, NULL, NULL);

    .. group-tab:: C++

		.. code:: C++
			
			dds::domain::DomainParticipant participant(5);

    .. group-tab:: Python

		.. code:: Python

			dp = DomainParticipant(5)

.. important::
	You must have the same ID on both the reading side and the writing side, otherwise, 
	they can not see each other.