In the previous chapter, we learned how to install ROS. Subsequently, in this chapter, we will look into the ROS architecture and concepts along with its components. Furthermore, we will learn how to create and use the ROS components—nodes, packages messages, services, and much more, with examples.

The ROS architecture and design has been divided into three sections or levels of concepts:

• The ROS filesystem: In this level, a group of concepts is used to explain how ROS is internally formed, the folder structure, and the minimum number of files that it needs to work.
• The ROS computation graph: In this section, we will see all the concepts and mechanisms which are required to set up the ROS computational network and environment, handle all the processes, and communicate with more than a single computer, and so on.

• The ROS community: This level is of great...

The main purpose of the ROS filesystem is to centralize the build process of a project, while at the same time providing enough flexibility to decentralize its dependencies. Nevertheless, the ROS filesystem is one of the important concepts to understand while developing projects in ROS, but, with time and patience, the developer will easily become familiar with it and realize its usefulness in managing complex projects and their dependencies:

Similar to an operating system, an ROS filesystem is divided into folders, and these folders have files that describe their functionalities:

• ROS Packages: The ROS software is organized in the form of packages, as...

ROS creates a computational network where all the processes are connected. Any process in the system can access this network, interact with other processes, observe the information that they are sending, and transmit data to the network. In general, they perform collaborative computational tasks.

This computation network can be called the computation graph. The basic concepts in the computation graph are ROS nodes, master, parameter server, messages, topics, services, and bags. Each concept in the computational graph has a specific contribution in different ways.

The ROS communication-related packages, including core client libraries, such as roscpp and rospython, and the implementation...

ROS is a large project that has many ancestors and contributors. The need for an open collaboration framework was felt by many people in the robotics research community. The effort was boosted by countless researchers who contributed their time and expertise to the core of ROS and its fundamental software packages. Throughout, the software was developed in the open using the permissive BSD open source license, and it gradually became widely used in the robotics research community.

The ROS ecosystem now consists of tens of thousands of users worldwide, working in domains ranging from tabletop hobby projects to large industrial automation systems.

The ROS community-level concepts...

In the preceding section, we learned about the basic concept and terminology required to start with the ROS computational network framework. Subsequently, in this section, we will focus mostly on the practical aspect.

Before running any ROS nodes, we should start the ROS master and the ROS parameter server. We can start ROS master and the ROS parameter server using a single command called roscore, which will start three programs by default; ROS master, ROS parameter server, and rosout logging nodes.

It is time for...