5.2. Configuring ROS 2 Topic and Type Aliasing in Connext

Connext-only applications using 7.5.0 or later can enable topic aliasing with the following properties.

5.2.1. dds.ros.enable_interoperability

Default: False

The dds.ros.enable_interoperability property enables ROS 2 topic and type mangling in Connext as described in Understanding Topic and Type Aliasing. When this property is set to true on the participant QoS, all entities created by that participant will have topic and type mangling enabled. When set on the writer or reader QoS, only writers or readers loading that QoS profile for which the property is enabled will have topic and type mangling enabled. The value set in the writer or reader QoS overrides the value set in the participant QoS, if it is set in both places.

Here is an example XML snippet that sets the property to true:

<property>
    <value>
        <element>
            <name>dds.ros.enable_interoperability</name>
            <value>true</value>
        </element>
    </value>
</property>

5.2.2. dds.ros.use_mangled_names_as_default

Default:

• True when dds.ros.enable_interoperability is true

• False when dds.ros.enable_interoperability is false

The dds.ros.use_mangled_names_as_default property configures whether the Connext topic name is announced as the primary topic name or as a topic alias, as well as whether the Connext type name is announced as the primary type name or as a type alias. See Understanding Topic and Type Aliasing.

See Enabling Connext 7.5.0 or Later with any ROS RMW for brief tutorials on enabling ROS 2 topic aliasing in your Connext applications. (The tutorials quickly guide you through both setting the property and getting the endpoints to communicate.)

Attention

For the purposes of this scenario (Enabling Connext 7.5.0 or Later with any ROS RMW), leave this property set to true.

When this property is set to true, Connext applications will announce the mangled ROS 2 topic name as the primary topic name and announce the Connext topic name as a topic alias. This allows Connext 7.5.0-and-later applications to communicate with ROS 2 applications with any RMW, which is the scenario we are documenting in Enabling Connext 7.5.0 or Later with any ROS RMW.

Note that setting this property to true—although enabling communication between ROS 2 and Connext 7.5.0-and-later applications—precisely prevents communication with Connext applications before 7.5.0. This is because applications before 7.5.0 use the Connext topic name and don’t recognize topic aliases. So, when this property is set to true, a Connext 7.5.0-and-later application with topic “Foo” can communicate with a ROS 2 application with topic “Foo”, but cannot communicate with a Connext 7.3.0 application with topic “Foo.”

Conversely, when dds.ros.use_mangled_names_as_default is set to false, Connext applications will announce the Connext topic name as its primary topic and announce the mangled ROS 2 topic name as its topic alias. This allows Connext applications to communicate with Connext applications before 7.5.0, but prevents communication with ROS 2 applications—unless those ROS 2 applications are using a Connext RMW with a 7.5.0-or-later version of Connext. A 7.5.0-or-later Connext RMW can handle both the primary topic and topic alias, thus enabling communication even when dds.ros.use_mangled_names_as_default is set to false. (Using the Connext RMW with a 7.5.0-or-later version of Connext is currently experimental.)