How do I troubleshoot ROS 2 communication issues between Simulink and Foxy in R2022b?

I have created a publisher with a custom topic called "my_topic" using Simulink:

In MATLAB R2022b, I am able to see the topic by executing the following command

ros2 topic list

which produces the following output

/my_topic
/parameter_events
/rosout

However, I am unable to see "my_topic" when using the same command in the ROS 2 Foxy command prompt.

How can I see "my_topic" from the command prompt?

Answer 1

[MathWorks Support Team]

In order to troubleshoot the issue, you can follow the steps below:

1) Confirm that "ROS_DOMAIN_ID" is set to 112 from both the MATLAB R2022b Command Window and the ROS 2 Foxy command prompt.

In particular, using the ROS 2 Foxy command prompt, set "ROS_DOMAIN_ID" outside MATLAB using the command

set ROS_DOMAIN_ID=112

and then check that the ID is correctly set using the command

echo %ROS_DOMAIN_ID%

Then, to see the list of topics in the ROS 2 Foxy command prompt, execute the command

ros2 topic list

a few times in case you do not see topics for the first time on that particular domain ID.

2)  If the topic list still does not contain the topic of interest "my_topic", execute the following commands in the ROS 2 Foxy command prompt

ros2 daemon stop 
ros2 topic list

to see if the topic appears in the list.

3)  If the topic list still does not contain the topic of interest "my_topic", delete all possible files from the folder where the ROS 2 Fast-DDS specific cache files are located. Ignore the ones that cannot be deleted, as they are locked by the ROS 2 node running in MATLAB R2022b.

Then, in the ROS 2 Foxy command prompt execute the commands below

ros2 daemon stop
ros2 topic list

to see if the topic appears in the list.