ROS Discovery Server

The ROS discovery server facilitates communication between different ROS2 nodes. It acts as a central point for nodes to discover each other on the network.

⚠️ Important If you are using your robot at our Rose City Robotics Lab, a discovery server is already running on the lab network. You can skip this step if you have not yet modified this file for your home setup.

Run your own discovery server

If you want to be able to run your robot on your own, without the RCR discovery server, you will need to follow these steps:

Note the IP Address

127.0.0.1 for local host (your own machine)

Start the Discovery Server

Open a new terminal window 📟

fastdds discovery --server-id 0

This command initiates the Fast DDS discovery server with a server ID of 0.

Update Configuration File

Open a new terminal window 📟

nano ~/ros2_ws/super_client_configuration_file_rcr.xml

<profiles xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles">
  <participant profile_name="super_client_profile" is_default_profile="true">
    <rtps>
      <builtin>
        <discovery_config>
          <discoveryProtocol>SUPER_CLIENT</discoveryProtocol>
          <discoveryServersList>
            <locator>
              <udpv4>
                <address>127.0.0.1</address>
                <port>11811</port>
              </udpv4>
            </locator>
          </discoveryServersList>
        </discovery_config>
      </builtin>
    </rtps>
  </participant>
</profiles>

Edit line 11 of the super_client_configuration_file_rcr.xml file to set the discovery server’s address to 127.0.0.1 if running locally.

Start the Micro ROS Agent

cd ~
SERIAL_TEENSY_DEVICE=`find /dev/serial/by-id/ -name "usb-Teensyduino*if00"|head -1`
sudo docker run -it --rm -v /dev:/dev --privileged --net=host --env-file ./env.list --name agent microros/micro-ros-agent:kilted serial --dev ${SERIAL_TEENSY_DEVICE} -v4

Update DDS Configuration in Container

Open a new terminal window 📟

sudo docker cp ~/ros2_ws/super_client_configuration_file_rcr.xml agent:/uros_ws/
sudo docker commit agent microros/micro-ros-agent:kilted

Restart the micro ros agent after updating the configuration file inside the container ( in the terminal window 📟 that is running the agent. You can use the up arrow to repeat the sudo docker run command).

Verification

To verify the discovery server is working:

# Check if discovery server is running
ps aux | grep fastdds

# Check network connectivity
ping 127.0.0.1

Switch back to RCR discovery server

If you have updated your discovery server settings above to use your robot at home, you will need to follow the steps below

Note the IP Address

192.168.1.125 for Joe’s laptop at RCR Lab

Update Configuration File -

Open a new terminal window 📟

nano ~/ros2_ws/super_client_configuration_file_rcr.xml

<profiles xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles">
  <participant profile_name="super_client_profile" is_default_profile="true">
    <rtps>
      <builtin>
        <discovery_config>
          <discoveryProtocol>SUPER_CLIENT</discoveryProtocol>
          <discoveryServersList>
            <locator>
              <udpv4>
                <address>192.168.1.125</address>
                <port>11811</port>
              </udpv4>
            </locator>
          </discoveryServersList>
        </discovery_config>
      </builtin>
    </rtps>
  </participant>
</profiles>

Edit line 11 of the super_client_configuration_file_rcr.xml file to set the discovery server’s address to 192.168.1.125 for Joe’s computer

Start the Micro ROS Agent

cd ~
SERIAL_TEENSY_DEVICE=`find /dev/serial/by-id/ -name "usb-Teensyduino*if00"|head -1`
sudo docker run -it --rm -v /dev:/dev --privileged --net=host --env-file ./env.list --name agent microros/micro-ros-agent:kilted serial --dev ${SERIAL_TEENSY_DEVICE} -v4

Update DDS Configuration in Container

Open a new terminal window 📟

sudo docker cp ~/ros2_ws/super_client_configuration_file_rcr.xml agent:/uros_ws/
sudo docker commit agent microros/micro-ros-agent:kilted

Restart the micro ros agent after updating the configuration file inside the container ( in the terminal window 📟 that is running the agent. You can use the up arrow to repeat the sudo docker run command).

Verification

To verify the discovery server is working:

# Check if discovery server is running
ps aux | grep fastdds

# Check network connectivity
ping 192.168.1.125

Common Issues

Discovery server not starting:

Check if port 11811 is available
Verify Fast DDS is properly installed
Check network connectivity

Nodes not discovering each other:

Verify the configuration file has the correct IP address
Check that all nodes are using the same discovery server
Ensure firewall settings allow ROS2 communication

Micro ROS agent connection issues:

Verify the Teensy device is connected
Check the serial device path
Ensure Docker has proper permissions

For keyboard teleoperation setup, see Keyboard Teleoperation For troubleshooting, see Troubleshooting