Is it possible to send and receive services?

[alexgiano]

Is it possible to send services via RPC calls? I saw that it is possible to exploit libraries like the following https://github.com/ika-rwth-aachen/mqtt_client to send asynchronous messages and wait for a response just like in ROS. For my project it is essential to use services to send commands to my robot. Thanks in advance

[lreiher]

Services and actions are not supported, although it should in principle be pretty straightforward to implement. You might want to consider https://github.com/eclipse-zenoh/zenoh-plugin-ros2dds.

[petergerten]

Any hints on what would need to be done to support services and actions? I think this would be very useful and only then makes it a full 'bridge' to ros2.

[lreiher]

I may have been a little too rash with my previous claim of straightforward implementation. ;)

Currently, the mqtt_client is using generic subscriptions and generic publishers for topics, see here. This allows us to work with arbitrary ROS message types at runtime.

Something similar would be needed for services and actions, however, I'm not aware of any rclcpp-functionality for generic services/actions. This is not to say that it's impossible, but would probably increase the implementation effort a lot.