Troubleshooting

Symptom: Two computers on the same network cannot see each other’s ROS 2 topics.

• ROS Environment
  • Are the ROS_DOMAIN_ID values the same across the running ROS programs?
• Networking

  • Is multicast working? Use the following commands on a single computer (and both computers) to see if multicast is working:

    ros2 multicast receive # on one terminal
    ros2 multicast send # in the other terminal
    

  • Are the firewalls up? Use sudo ufw status on each computer to see.

    • While you could disable the firewall, it is more secure to do the following:

      sudo ufw allow in proto udp to 224.0.0.0/4
      sudo ufw allow in proto udp from 224.0.0.0
      

      • This should persist across restarts.

  • Do you have multiple network interfaces? This can cause multicast to have issues.

    • Try sudo ip route add 224.0.0.0/4 dev <desired_network_interface_name>
      • This does not necessarily persist across restarts