FastDDS Discovery Server¶

Standard ROS2 relies on multicast for node discovery, which does not work across VPN tunnels or between machines on different networks. The solution is a centralized FastDDS Discovery Server running on the vehicle, which all nodes (local and remote) register with via unicast.

How it works¶

sequenceDiagram
    participant V as Vehicle PC
    participant DS as Discovery Server (port 11811)
    participant O as Remote Operator

    V->>DS: register nodes (local, via 127.0.0.1 or wt0)
    O->>DS: register nodes (via NetBird IP)
    DS-->>V: peer list
    DS-->>O: peer list
    V<-->>O: ROS2 topic exchange (unicast)

Setup on the vehicle¶

Dockerfile.server¶

FROM ros:humble-ros-core
RUN apt-get update && apt-get install -y \
    ros-humble-rmw-fastrtps-cpp \
    fastdds-tools \
    && rm -rf /var/lib/apt/lists/*
ENTRYPOINT ["fastdds", "discovery"]

docker-compose.yml (vehicle side)¶

services:
  discovery-server:
    build:
      context: .
      dockerfile: Dockerfile.server
    container_name: fastdds_server
    network_mode: "host"        # must use host to reach NetBird wt0 interface
    command: -i 0               # discovery server ID 0
    restart: unless-stopped

Start it:

docker compose up -d discovery-server

Or without Docker:

source /opt/ros/humble/setup.bash
fastdds discovery -i 0

GigE camera conflict

Running the Discovery Server without binding it to a specific interface caused it to advertise on the camera's GigE interface (169.254.x.x), blocking camera connections. Using network_mode: host combined with the NetBird-only FastDDS profile resolves this.

Environment variables¶

Vehicle side¶

# No special discovery server env needed — it's the server itself
ROS_DOMAIN_ID=0
RMW_IMPLEMENTATION=rmw_fastrtps_cpp

Operator side¶

export ROS_DISCOVERY_SERVER=twizy:11811   # NetBird hostname of the vehicle
export ROS_SUPER_CLIENT=true              # disables multicast, forces Discovery Server usage
export ROS_DOMAIN_ID=0
export RMW_IMPLEMENTATION=rmw_fastrtps_cpp

Variable	Value	Description
`ROS_DISCOVERY_SERVER`	`twizy:11811`	NetBird hostname (or IP) of the vehicle running the server
`ROS_DOMAIN_ID`	`0`	Must be identical on all machines in the network
`ROS_SUPER_CLIENT`	`true`	Disables multicast, forces exclusive use of Discovery Server
`RMW_IMPLEMENTATION`	`rmw_fastrtps_cpp`	Sets FastDDS as the ROS2 middleware

Verification¶

# On any machine with the env vars set:
ros2 topic list
# Should show topics from the vehicle