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Version: 7

Networking and PC Setup Troubleshooting

Multiple computer setup cannot communicate via DDS​

Problem: In a multiple computer setup, I can ping the other computer but can't communicate with it via ros2 run demo_nodes_py talker + ros2 run demo_nodes_py listener

Solution: Check that your network interface adapter and peer address entries for your method of configuring DDS are correct as explained in the DDS configuration docs.

Multiple computer setup error messages that "Action server not available"​

Problem: Multiple computers are connected over the network, but the agent cannot seem to access action servers or services provided by the robot drivers, or discover controllers, resulting in errors such as:

[ERROR] [1658269925.062171689] [MoveGripperAction]: Error code: -25; Message: Failed to send trajectory execution action goal to server.; Details: Action server not available.
...
[ERROR] [1658269931.800549146] [Teleoperate]: Error code: 99999; Message: Failed to enable required controller servo_controller; Details: Service /ensure_controller_is_active failed with message: Failed to ensure that specified controllers are active.
...
[ERROR] [1658269939.054476603] [moveit_ros.trajectory_execution_manager]: Controller '/joint_trajectory_controller' is not known

Solution: Check that your network interface adapter and peer address entries for your method of configuring DDS are correct as explained in the DDS configuration docs.

Multiple computer setup does not have synchronized clocks​

Problem: When using multiple computer setups, the computers' clocks go out of sync. This can been seen by messages arriving from the future. Or TF complaining about old messages.

Solution: To solve this, one or both of the machines should install chrony:

sudo apt-get install chrony

If any machine in the setup does not have access to NTP, the machine that has chrony installed can serve as a NTP server. Suppose the drivers RTPC does not have an internet connection, but has a direct link to the agent PC. On the main PC (usually the PC running the Agent), install chrony and then add lines to /etc/chrony/chrony.conf to allow the drivers RTPC to connect to it. For example:

# Allow drivers PC to use the agent PC as NTP server
allow 192.168.1.2  # This should be the IP address of drivers RTPC

Then restart the service:

sudo systemctl restart chrony.service

On the drivers RTPC, reconfigure timesyncd to use the agent PC as an NTP server. Modify /etc/systemd/timesyncd.conf to have:

[Time]
# Use the Agent PC as the primary NTP source
NTP=192.168.1.1  # This should be the IP address of the agent PC

And restart the service:

sudo systemctl restart systemd-timesyncd.service