OK, now we're really starting to get moving with XMPP and we still haven't even begun to scratch the surface. In this chapter, we're going to start increasing our speed towards 88 mph! Maybe not quite, but we are going to introduce a very important area of XMPP (something from which many, many other protocols and projects are built), and that's Publish-Subscribe, or pubsub for short. The original pubsub specification was documented in XEP-0060 (http://www.xmpp.org/extensions/xep-0060.html) and, while having some extensions, has remained fairly solid. So once we've covered some basics, we're just going to dive right into some practical work and learn how to make our static website real-time with very little code or effort using XMPP.

Pubsub is used extensively by many different companies in many different sectors. For example, it is often used to build real-time monitoring systems, social networks, and Internet of Things (IoT) setups, often with...