Dive into the fourth lesson of the ROS 101 tutorial series, focusing on ROS services and the client-server architecture. Learn the differences between client-server and publisher-subscriber models, and gain hands-on experience creating client and server packages in ROS. Explore various architectures in ROS packages, master client-server programming techniques, and understand how to troubleshoot common issues. This comprehensive one-hour video tutorial includes a quick recap of previous lessons, an in-depth explanation of ROS services, and practical demonstrations to reinforce your understanding of these essential concepts in robotics and mechatronics.