ROS 2 Interoperability

nros communicates with standard ROS 2 nodes via rmw_zenoh_cpp. Both sides connect to the same zenohd router (or peer directly).

Quick Start (3 Terminals)

# 1. Start zenoh router
zenohd --listen tcp/127.0.0.1:7447
 
# 2. Run the nros C talker (see Getting Started for build steps)
./my_c_talker
 
# 3. Run a ROS 2 listener
source /opt/ros/humble/setup.bash
export RMW_IMPLEMENTATION=rmw_zenoh_cpp
ros2 topic echo /chatter std_msgs/msg/Int32 --qos-reliability best_effort

Requirements

• RMW implementation: set RMW_IMPLEMENTATION=rmw_zenoh_cpp on the ROS 2 side.
• QoS: nros defaults to BEST_EFFORT reliability. Pass --qos-reliability best_effort on the ROS 2 subscriber, or configure both sides to use RELIABLE.
• zenohd version: both zenoh-pico (used by nros) and zenohd must be the same version. Version mismatches cause transport failures.

Common Issues

• Topic not visible in ros2 topic list — nros must declare liveliness tokens (handled automatically by the transport layer). Verify zenohd is reachable from both sides.
• No messages received — check that the data key expression uses TypeHashNotSupported (Humble) not RIHS01_… in the data topic. This is handled automatically when using the ros-humble feature.
• QoS mismatch — nros defaults to BEST_EFFORT; pass --qos-reliability best_effort on the ROS 2 subscriber.
• rmw_zenoh not connecting — force client mode on the ROS 2 side:

  export ZENOH_CONFIG_OVERRIDE='mode="client";connect/endpoints=["tcp/127.0.0.1:7447"]'

• Humble vs Iron — Humble uses TypeHashNotSupported; Iron+ uses RIHS01_<sha256> (requires building with the ros-iron feature).