4 Turtlesim

Open 2 terminals.

First terminal: roscore

Second terminal:

rosrun turtlesim turtlesim_node

Then type

rosnode info turtlesim

You'll be able to see information about this node - Publications/Subscriptions/Services

 

rostopic list
rostopic echo [one of the topics on the list]

this will show information about turtlesim

Reference: https://wiki.ros.org/ROS/Tutorials/UnderstandingNodes