What is XMPP?

XMPP is used to solve many real-world problems and has made its way into many large services, often without users realizing. Some large examples of deployments or XMPP-based services include:

Additionally, many services also allow users to connect via an XMPP gateway, meaning that users can connect with their preferred clients rather than with those supplied by a company, such as Slack and Skype.

XMPP is deployed in many industries where its uses go beyond simple chat applications to include diverse purposes such as the following:

With the continuing rise of the real-time web and WebRTC applications, XMPP is becoming more relevant on the web than ever before. Its push architecture means that lightweight real-time applications can be built without continuously polling the server, making for more scalable web applications. Its mature standards mean that developers are quickly able to build real-world applications without having to design their own proprietary standards and benefit from the thought and problem solving that has gone into XMPP.

With all its advantages, one area that WebRTC hasn't solved (nor was it designed to solve) is the issue of session negotiation. Not only was a standard called Jingle available in XMPP before WebRTC arrived in the browser, but also it turns out that it's a great way of transferring session data to form peer-to-peer sessions. This means that users are now able to use WebRTC clients of their choice without having to visit and reply upon a meet me type URL or a proprietary signaling method.

Node.js was released in 2009, and since its release, it has quickly become a nearly indispensable tool for server side development using JavaScript. Node.js allows developers to create fast and scalable applications (especially when asynchronous IO libraries are used) in a single language throughout an application's stack, with JavaScript running on both the back-end and front-end.

While Node.js is not required for working with XMPP, all examples in this book will utilize libraries written in Node.js, some of which can also run on the browser.

Using Ubuntu 16.04 as a base, we're now going to install Node.js and some core dependencies for the libraries we'll be using.

First we'll install libicu-dev and libexpat-dev. These libraries allow us to perform case transformations on international characters and process XML, respectively:

$ sudo apt-get install libicu libexpat1-dev

Next, we'll work on installing Node.js itself. My preferred method of achieving this is to use nvm by Tim Caswell, which is available from this GitHub repository: https://github.com/creationix/nvm . Please check out the readme for the current installation instructions, but at the time of writing this book, the procedure is as follows:

$ curl https://raw.githubusercontent.com/creationix/nvm/v0.32.0
    /install.sh | bash
$ source ~/.bashrc
$ nvm install 6
$ node -v

This will install the latest version of the Node.js 6 release for you. The advantage of using nvm over the operating system packages is that it is easy to switch between different versions of Node.js with a simple command.