Socket.io is a library used for creating real-time web applications. It exploits WebSockets, which allows real-time and bi-directional communication. When WebSockets are not available, it utilizes old-fashioned technologies such as long polling, which simulates real-time communication. As a result, the application runs on the older browsers and a developer has one consistent interface. Subsequently, Socket.io simplifies the real-time application development process. Combining great idea with such advanced tool will let us create extraordinary software, which will stay modern for a long time.