Extensible Messaging and Presence Protocol (XMPP) is a communication protocol that provides near-real-time message passing between two or more entities. XMPP is based on XML and transfers data in predefined formats that are known to server as well as client systems. Being an XML-based protocol, you can easily extend XMPP to suit your requirements. It also provides various standard extensions to extend the base functionality of the XMPP server.

In this chapter, we will learn how to set up our own XMPP server. The main focus will be on implementing a simple chat application. In later recipes, we will also look at a Node.js and socket-based alternative to implementing the messaging server.

We will be working with a popular XMPP server Ejabberd. It is a well-known XMPP implementation supported by ProcessOne. Ejabberd is based on Erlang, a functional programming language specifically designed for soft real-time communication.