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, application runs on the older browsers and a developer has one consistent interface. Subsequently, Socket.io simplifies 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.