A minimal ROS 2 Jazzy + rosbridge + roslibjs demo with a Start/Stop custom message.

Minimal demo to:

• build a custom ROS 2 message my_msgs/msg/Command
• run rosbridge (WebSocket gateway) in Docker
• publish Start/Stop from a web page (roslibjs)
• run a Python listener node (my_controller/command_listener) that logs received commands

rosbridge-web-demo/
├─ docker-compose.yml
├─ .dev/
│  ├─ Dockerfile
│  └─ entrypoint.sh      # loads ROS + overlay in all containers      
├─ index.html            # webpage using roslibjs
└─ src/
   ├─ my_controller/
   └─ my_msgs/

From the repo root:

docker compose up -d --build
docker compose ps

Services:

• ros – dev shell with your workspace mounted at /ws
• rosbridge – WebSocket server on localhost:9090
• listener – runs my_controller/command_listener (after the workspace is built)

If listener logs “No executable found” or “Package not found”, see Troubleshooting.

Open a shell in the dev container, build, and load the overlay:

docker compose exec ros bash
# inside container
source /opt/ros/jazzy/setup.bash
cd /ws
rosdep install --rosdistro jazzy --from-paths src -i -y
colcon build --symlink-install --merge-install
source /ws/install/setup.bash
ros2 interface show my_msgs/msg/Command
# expect:
# uint8 START=1
# uint8 STOP=2
# uint8 command
exit

Restart services that need to see the new interfaces:

docker compose restart rosbridge listener

Open index.html in your browser (double-click is fine).

• It connects to ws://localhost:9090.
• Click Start / Stop to publish Command messages (command=1/2) to /my_robot/command.

To watch messages in a terminal (optional):

docker compose exec ros bash -lc "source /ws/install/setup.bash && ros2 topic echo /my_robot/command"

docker compose logs -f listener

The Compose service listener runs the Python node that subscribes to /my_robot/command and logs:

[INFO] [command_listener]: Received: START
[INFO] [command_listener]: Received: STOP

docker compose exec ros bash
# inside
source /opt/ros/jazzy/setup.bash
source /ws/install/setup.bash
ros2 pkg executables | grep my_controller
ros2 run my_controller command_listener.py   # or 'command_listener' if you installed without .py

# Open a dev shell
docker compose exec ros bash

# Tail rosbridge logs
docker compose logs -f rosbridge

# Confirm rosbridge port
docker compose port rosbridge 9090   # -> 0.0.0.0:9090

# Stop stack
docker compose down

“Package ‘my_controller’ not found” (listener)
Cause: service commands don’t read ~/.bashrc. We fix this via entrypoint.sh which sources ROS and /ws/install for every container command; still, the workspace must be built at least once.

• Build once:

  docker compose exec ros bash -lc "source /opt/ros/jazzy/setup.bash && cd /ws && colcon build --symlink-install --merge-install"
  docker compose restart listener

• Sanity check:

  docker compose exec ros bash -lc "source /ws/install/setup.bash && ros2 pkg list | grep my_controller"

“No executable found” (listener)
Your installed executable is likely command_listener.py. Either:

• Run with suffix in compose:

  command: ros2 run my_controller command_listener.py

• Or install without suffix. In src/my_controller/CMakeLists.txt:

  install(PROGRAMS
    scripts/command_listener.py
    DESTINATION lib/${PROJECT_NAME}
    RENAME command_listener
  )

  Rebuild, then use:

  command: ros2 run my_controller command_listener

Browser can’t connect to rosbridge
Ensure only rosbridge maps port 9090:9090 in docker-compose.yml. If 9090 is in use:

lsof -iTCP:9090 -sTCP:LISTEN
docker compose down && docker compose up -d

Unknown message my_msgs/msg/Command
Rebuild and re-source:

docker compose exec ros bash -lc "source /opt/ros/jazzy/setup.bash && cd /ws && colcon build --symlink-install --merge-install && source /ws/install/setup.bash && ros2 interface show my_msgs/msg/Command"
docker compose restart rosbridge listener

• The entrypoint ensures any service (listener, rosbridge, etc.) runs with the correct environment:

  #!/usr/bin/env bash
  set -e
  source /opt/ros/jazzy/setup.bash
  if [ -f /ws/install/setup.bash ]; then
    source /ws/install/setup.bash
    case ":$AMENT_PREFIX_PATH:" in *:/ws/install:*) ;; *) export AMENT_PREFIX_PATH="/ws/install:${AMENT_PREFIX_PATH:-}";; esac
    case ":$CMAKE_PREFIX_PATH:" in *:/ws/install:*) ;; *) export CMAKE_PREFIX_PATH="/ws/install:${CMAKE_PREFIX_PATH:-}";; esac
  fi
  exec "$@"

• index.html uses ws://localhost:9090. If you ever serve it via https, browsers may block ws://; use wss:// with TLS or serve the page over http:// during development.

Happy bridging!