This book systematically discusses the OCF IoT Protocol and open source design methods. Based on the core OCF resources, this book describes the use of the OCF Protocol in simple terms, and employs real cases to introduce the application of intelligent hardware in IoT. In the development process of IoT technology, the use of OCF protocol and platform will greatly improve the efficiency. The main content of this book is as follows: Overview of the Development of IoT (introducing the IoT generation, architecture, technology and development); Basic Principles of OCF Technology (elucidating the OCF technological framework and core functions); OCF Resource Model (describing the definition and operation of OCF resource, functional interaction and message passing method); Specific OCF Development Methods (based on Mac, Windows, Linux, Android and Arduino), this part mainly describes software tools, compilation methods, example codes and comprehensive examples.