In this chapter, we will build an implementation of the classic game Pong, using XMPP chat messages to communicate the position of the paddles and ball between clients. The game will be based on the XMPP-FTW skeleton and will draw to an HTML canvas. The intention of this chapter is to illustrate one way in which you could use XMPP to power your own user-centered applications. Specifically, in this chapter we take a very basic approach of sending application updates via the body of basic chat messages. In the next chapter, we will take a different approach of creating our own messages to share between the client and a custom server component which we will build; the approach taken in this chapter is to teach you how to build an application (ok, game) on XMPP using its core functionality before we extend things later.

Why base this demonstration on Pong? For one thing, Pong uses basic visualizations, so we can focus on the XMPP communication...