Real-time web applications

This paper discusses real-time web applications. Its main purpose is to familiarize the reader with the term "real-time web application" and the technologies behind creating real-time web applications with an emphasis on a practical demonstration. The first chapter is about the history of World Wide Web, the description of the HTTP protocol and the definition of real-time web applications. The second chapter describes the technologies used in other parts of the work, mainly their implications and usage in developing real-time web applications. Technologies like JavaScript, JSON, Ajax (XHR, JSONP), jQuery library and server solution Node.js will be mentioned. The third chapter is the major part of the paper. It deals with the techniques of a real-time client communicating with the server, also called transport models. Each technique and its description is accompanied by a picture showing the client's communication with the server and an example source code. At the end of the third chapter, the solutions mentioned are widely used by programmers, specifically the Ajax Push Engine (APE), the Socket.IO library and the service Pusher.com. The fourth, the last chapter of the paper, contains a description of the demonstration web application created for the purpose of this work - a multi-user group chat. It is mainly a description of its features and how you prepare an environment to run real-time web applications. It also contains a tutorial how to create a basic "skeleton" for real-time web application using Node.js server solution, Express framework and Socket.IO library. The source code of the sample application is located on the enclosed DVD, and digitally as an attachment on the VSE information system and it is also uploaded at Github. The main contribution of this paper is to provide a comprehensive and coherent description of technologies behind creating real-time web applications with a provided example source code for a demonstration for each technique