Using Zenoh with the Simulator

This guide configures the Clearpath simulator to use rmw_zenoh_cpp without connecting it to physical robots. It assumes the simulator and Zenoh packages are installed. For router design and intentional connections to other robots, see the Zenoh ROS middleware guide.

Configure the simulator

Use a separate setup directory for simulation so its configuration does not overwrite the configuration used by a physical robot or another setup.

mkdir -p ~/clearpath_sim

Copy a valid Clearpath robot.yaml into the new directory. In ~/clearpath_sim/robot.yaml, configure Zenoh under the existing system: key. Use a unique namespace and a domain ID separate from the physical fleet. For example, if physical robots use domain 26, use 27 for the simulator:

system:
  hosts:
    - hostname: a300-sim # cannot contain characters other than [A-Z][a-z][0-9] and -
  ros2:
    namespace: a300_sim
    domain_id: 27
    middleware:
      implementation: rmw_zenoh_cpp

Keep ros2 and any other settings in the same system: mapping. Do not add a custom middleware.profile for this isolated simulator setup. The default router configuration has no outbound connections to the physical robots.

Install the Zenoh RMW package if it is not already installed:

sudo apt update
sudo apt install ros-jazzy-rmw-zenoh-cpp

Start the router

The simulator launch starts Gazebo and the ROS-Gazebo bridge; start a standalone Zenoh router separately and leave it running while using the simulation. Use the default router configuration and clear any inherited Zenoh overrides:

source /opt/ros/jazzy/setup.bash
export RMW_IMPLEMENTATION=rmw_zenoh_cpp
export ROS_DOMAIN_ID=27
unset ZENOH_CONFIG_OVERRIDE
unset ZENOH_ROUTER_CONFIG_URI
ros2 run rmw_zenoh_cpp rmw_zenohd

This router uses the default configuration and does not connect to the physical robots. Router configuration and intentional multi-robot connection examples are in the Zenoh ROS middleware guide.

Launch the simulation

In a second terminal, source ROS and set the same RMW and domain before launching the simulator. The simulator launch generates robot launch and parameter files, but does not create ~/clearpath_sim/setup.bash:

source /opt/ros/jazzy/setup.bash
export RMW_IMPLEMENTATION=rmw_zenoh_cpp
export ROS_DOMAIN_ID=27
unset ZENOH_CONFIG_OVERRIDE
unset ZENOH_ROUTER_CONFIG_URI
echo "$ZENOH_CONFIG_OVERRIDE"
echo "$ZENOH_ROUTER_CONFIG_URI"
ros2 launch clearpath_gz simulation.launch.py setup_path:=$HOME/clearpath_sim

Both echo commands should print empty lines. This ensures the simulator uses the local default Zenoh router and does not inherit a client connection to a physical robot.

Configure ~/clearpath_sim/robot.yaml with rmw_zenoh_cpp, a unique namespace, and a domain ID separate from the physical robots. For example, keep the simulator on domain 27 when the physical robots use domain 26; different domains prevent their ROS traffic from mixing. The unique namespace, such as a300_sim, makes simulator topics easy to distinguish.

Verify communication

In a third terminal, set the same RMW and domain, then list topics under the simulator namespace:

source /opt/ros/jazzy/setup.bash
export RMW_IMPLEMENTATION=rmw_zenoh_cpp
export ROS_DOMAIN_ID=27
unset ZENOH_CONFIG_OVERRIDE
unset ZENOH_ROUTER_CONFIG_URI
ros2 daemon stop
ros2 topic list | grep '^/a300_sim/'

The list should include simulator topics, such as /a300_sim/platform/odom/filtered, as well as /parameter_events and /rosout. Verify data is arriving on an active topic:

ros2 topic echo /a300_sim/platform/odom/filtered

The exact available topics depend on the selected platform and running simulator plugins.

Troubleshooting

• The launch reports Middleware profile path ... does not exist. Remove the custom system.ros2.middleware.profile setting from the simulator's robot.yaml for this isolated setup. Also unset ZENOH_ROUTER_CONFIG_URI before starting the router and simulator.

• Only /parameter_events and /rosout appear. Confirm the router is still running and that each simulator terminal uses rmw_zenoh_cpp and domain 27, and that both Zenoh overrides are unset. The simulator launch does not generate ~/clearpath_sim/setup.bash; set the environment in each terminal as shown above.

• The simulator discovers physical robot topics. Stop the simulator and its router, remove custom router profiles and Zenoh overrides, then restart both with domain 27. Keep physical robots on their separate domain 26.

• Gazebo repeatedly reports it is waiting for robot_description, and no robot appears. Check the launch terminal's Zenoh variables. If ZENOH_CONFIG_OVERRIDE points to a physical robot, simulator nodes try to connect there instead of the local router; the robot description publisher can fail before Gazebo spawns the model. Stop the simulator, unset both Zenoh overrides, confirm they print empty, and relaunch with domain 27:

  unset ZENOH_CONFIG_OVERRIDE
  unset ZENOH_ROUTER_CONFIG_URI
  echo "$ZENOH_CONFIG_OVERRIDE"
  echo "$ZENOH_ROUTER_CONFIG_URI"
  export RMW_IMPLEMENTATION=rmw_zenoh_cpp
  export ROS_DOMAIN_ID=27
  ros2 launch clearpath_gz simulation.launch.py setup_path:=$HOME/clearpath_sim

• ros2 reports an undefined Zenoh symbol. Check that ros-jazzy-rmw-zenoh-cpp and ros-jazzy-zenoh-cpp-vendor are compatible and installed from the configured ROS repository.