Carla 0.9.16 ROS2 Native: support alternative DDS implementations

[maxime-clem]

Is your feature request related to a problem? Please describe.
The current ROS2 native implementation for Carla 0.9.16 only supports eProsima’s Fast DDS.

Describe the solution you'd like
The DDS used by Carla 0.9.16 can be configured and different implementations can be used.

Describe alternatives you've considered
Changing the DDS implementation used on my system.

Additional context
ROS2 allows using alternative DDS implementations. For example CycloneDDS is used in Autoware.

[ali-0-1]

Same is true for Carla 0.10.0.
Due to fastdds implementation we could not get topics from the vehicle which is using cyclonedds. Carla is dominating the communication, exporting cyclonedds also has no effect.
Is there any work around or implementation that can solve the issue?
For now, we used another machine in the same network which can access pyhtonApi of Carla and get data from the vehicle, that is the work around we found for now.

We have Ros2 humble installed in both machines and the vehicle.

[ali-0-1]

UPDATE:
Actually our case was not related to implementation type but network configuration and firewall settings. While the Carla and vehicle in the same network with proper settings they can communicate without additional implementation change.
Vehicle has cyclonedds implementation and Carla by default Fastdds.

[Edwardius]

Looking at the source code, fastdds looks extremely baked into its ros2 implementation. There doesn't seem to be an easy way to support other middlewares natively without either some hacky solution or a huge refactor.

The only alternative is to really just ditch it and build something of your own (correct me if I'm wrong). I really don't want to do that...

[yemreikiz]

Any updates on this? FASTRTPS discovery over network for multiple devices(i.e. simulation on one machine and navigation algorithm on another) is difficult if you want to use network whitelisting.(ROS2 Humble, ubuntu 20.04). CycloneDDS on the other hand, handles interface whitelisting consistently.

[JesusAnaya]

@maxime-clem @yemreikiz I have been working for a while on implementing CycloneDDS in Carla UE4. I think I'm very close to getting a stable version. Furthermore, I will prepare a PR with these changes to ue4-dev very soon. Additionally, this refactoring includes a new C++ interface in the Carla library to implement other DDS backends in a more structured and "easy" way. Probably at the end of this week, I can have it ready.

This is an example of my local dev environement.

[JesusAnaya]

Added PR, you can clone my branch and compile from it for testing.