nros C++ 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_cpp_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 set both sides to RELIABLE.
- zenohd version: zenoh-pico (used by nros) and zenohd must match versions exactly. Mismatches cause silent transport failures.
- Type hash: Humble uses
TypeHashNotSupported; Iron+ uses RIHS01_<sha256>. Build with the matching ros-humble / ros-iron feature.
Common Issues
- Topic not visible in
ros2 topic list — verify zenohd is reachable from both sides; nros declares liveliness tokens automatically.
- No messages received — check that the data key expression uses the correct type-hash variant for your ROS 2 distro.
- QoS mismatch — pass
--qos-reliability best_effort on the ROS 2 subscriber, or set both sides to RELIABLE explicitly.
- 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"]'
See Also
- ROS 2 Interoperability on the C-API side (same protocol, same router)
docs/reference/rmw_zenoh_interop.md in the nano-ros source tree for the full key-expression and protocol reference
