This document provides an introduction to software defined networking (SDN) using OpenFlow and the Ryu SDN framework. It discusses the basics of SDN and OpenFlow, how to set up an environment using Mininet and Ryu, and includes code examples for common OpenFlow messages like Packet In, Packet Out, and Flow Entry modification. The goal is to provide readers with a quick start on using OpenFlow and Ryu to experiment with SDN concepts.