DDS Router with ROS and flaky discovery

[johnny555]

Thanks for a great tool.

I'm using it to route data on a local LAN, but from inside a docker container on a Windows 11 host. I have to do this because Windows 11 doesn't support routing UDP into their virtual machines/docker containers. I'm building a ROS system, the robot is on the lan running Linux, but the human control (RVIZ) is inside the docker running windows. The problem I get is that ros2 topic list doesn't show all of the topics, and sometimes ros2 topic echo doesn't work.

I'm abit stuck trying to debug this. Any tips on how to debug it, or perhaps something I missed in the configuration would be helpful! Thanks!

dds-router config for docker running on Windows 11:

version: v3.0 # 0

# PARTICIPANTS
participants:
  - name: DDS_LAN_B
    kind: local
    domain: 0

  - name: WANClient # 6
    kind: wan-discovery-server # 7
    discovery-server-guid:
      id: 2 # 8
    connection-addresses: # 9
      - discovery-server-guid:
          id: 1 # 10
        addresses: # 11
          - ip: 192.168.1.122
            port: 11888
            transport: tcp

  - name: ServerROS2 # 5
    kind: local-discovery-server # 6
    discovery-server-guid:
      ros-discovery-server: true # 7
      id: 3 # 8
    listening-addresses: # 9
      - domain: localhost # 10
        port: 11311 # 11

  - name: EchoParticipant # 6
    kind: echo # 7
    discovery: true # 8
    data: false # 9
    verbose: false # 10

And config running on the robot:

version: v3.0 

participants:
  

  - name: DDS_LAN_A
    kind: local
    domain: 0

 
  - name: WANServerKrytn                                               
    kind: wan-discovery-server                                    
    discovery-server-guid:
      id: 1                                                       
    listening-addresses:                                
      - ip: 192.168.1.122                                
        port: 11888                                         
        transport: tcp            

If I go ros2 topic list on the robot I get:

/bond
/camera/color/camera_info
/camera/color/image_raw
/camera/color/metadata
/camera/depth/camera_info
/camera/depth/color/points
/camera/depth/image_rect_raw
/camera/depth/metadata
/camera/extrinsics/depth_to_color
/camera/extrinsics/depth_to_depth
/camera/imu
/cmd_vel
/controller_server/transition_event
/cost_cloud
/diff_drive_base_controller/cmd_vel_unstamped
/dynamic_joint_states
/evaluation
/global_costmap/costmap_raw
/global_costmap/published_footprint
/joint_state_broadcaster/transition_event
/joint_states
/joy
/joy/set_feedback
/local_costmap/clearing_endpoints
/local_costmap/costmap
/local_costmap/costmap_raw
/local_costmap/costmap_updates
/local_costmap/local_costmap/transition_event
/local_costmap/published_footprint
/local_costmap/voxel_grid
/local_plan
/map
/map_metadata
/marker
/parameter_events
/plan_smoothed
/pose
/received_global_plan
/robot_description
/rosout
/scan
/slam_toolbox/feedback
/slam_toolbox/graph_visualization
/slam_toolbox/scan_visualization
/slam_toolbox/update
/smoother_server/transition_event
/tf
/tf_static
/transformed_global_plan
/velocity_smoother/transition_event

but if I do the same in the Windows11 docker I get alot fewer results:

/camera/color/image_raw
/diff_drive_base_controller/cmd_vel_unstamped
/joint_states
/joy
/joy/set_feedback
/parameter_events
/rosout

[juanlofer-eprosima]

Hi @johnny555

Some comments and questions after having checked your config files:

• What is the purpose of ServerROS2?
• Have you actually deployed a discovery server network? I mean, if you what you are trying to accomplish is a point to point communication, using a wan participant (a.k.a initial peers) might be more suitable. Also, I would recommend using UDP transport unless TCP is required (e.g. if ports can only be opened in the server side).
• DDS-Router creates internal entities when a reader is created in one of its participants. This means that if for example the docker application creates writers for a certain topic but no readers, no entity for that topic will be created in the docker router and, as a consequence, in the robot router.
• Using ros2 topics list is not fully compatible with DDS-Router. The reason for this is that this ROS 2 utility relies on the creation of an internal entities graph, which is built upon discovery events and with information received at ad hoc metatraffic topics. So not seeing all topics with this command is somewhat to be expected.
• As for debugging alternatives to ros2 topics list:
  • EchoParticipant, as you already figured out. I would suggest having a participant of this kind in both routers, and only launch one of your applications at a time with both routers running.
  • Using visualization tools such as Fast-DDS-spy or Fast-DDS-Monitor.
  • For more advanced users, using CLI options -d --log-verbosity="Info" --log-filter="DDSPIPE|DDSROUTER" will activate the info logs. For this, it is required to compile with CMake variable -DLOG_INFO=ON

Hope you find this information useful.

[johnny555]

Hi @juanlofer-eprosima ,

Thanks for a great reply, its really helpful!

I'll respond to your points below:

• heh, yeah I was just trying to get things to work, I hoped that adding a local discovery server would make things work better. But I guess it is redundant.
• Good point, I'm trying to get a point-to-point connection happening, but have it go over TCP as the docker inside windows can't talk UDP through windows. I'll try out the WAN participant and see how it goes.
• Ah I see. So if I understand this correctly, I should be able to stand up RViz, which is basically a big topic reader. And DDS-router should route any topic it asks for (assuming that the robot is publishing it).
• I didn't know this about ros2 topic list. I must admit I had assumed that using ros2 topic list would be the right way to verify things were working.
• Thanks for these debugging tools, they look really helpful!

Ok, I'll have a go at using a wan participant instead and let you know how it goes :)