Working with Jaxl – A Networking Library in PHP – Part 1 – An Introduction, Philosophy and History

Development of Jaxl library started way back in December’07 while I was working on a self-initiated project called Gtalkbots. The project is now dead, if you are interested in knowing more about it go through Gtalkbots BlogSpot. Jaxl v1.x was first released in Jan’09 and about a year later in Aug’10 Jaxl v2.x was released. First two versions were released as JAbber XMPP Library for writing clients and external server components.

While working on my startup Jaxl – A Platform As A Service (PAAS) for developing real-time applications, I started experiencing v2.x limitations when my external server side components were unable to process XMPP packets at the speed they were sent by ejabberd server. I started restructuring and refactoring the library which gave birth to Jaxl v3.x. Since v3.x was initially being used for developing the entire infrastructure, it shaped up as a networking library in PHP with stable support for XMPP protocol. However, later I had to rewrite several infrastructure components in Erlang Programming Language due to several issues that PHP as a language couldn’t solve (after all PHP wasn’t made for such tasks). Finally in April’12, Jaxl v3.x was open sourced.

Jaxl v3.x is an asynchronous, non-blocking, event based networking library in PHP for writing custom TCP/IP client and server implementations. From previous versions, Jaxl library inherits a full blown stable support for XMPP protocol stack. In v3.0, support for HTTP protocol stack was also introduced. At the heart of every protocol stack sits a Core stack. It contains all the building blocks for everything that we aim to do with Jaxl library. Both XMPP and HTTP protocol stacks are written on top of the Core stack. Infact the source code of these protocol implementations knows nothing about the standard (inbuilt) PHP socket and stream methods.

Philosophy
Jaxl is designed to work asynchronously in a non-blocking fashion and provides an event based callback API. Now what does all that mean?

By non-blocking and asynchronous it means, when a library function like:
$jaxl->send($stanza); is called, it will return immediately i.e. this function call will NOT block any further execution of your application script until $stanza has actually been sent over the connected TCP socket. Infact, when this function is called, passed $stanza object is put into an output buffer queue, which will be flushed as and when underlying TCP socket is available for writes. Similarly, most of the available methods (wherever required and possible) inside Jaxl library are non-blocking and asynchronous in nature.

By event based callback API it means, application code will need to register/add callbacks over necessary events as they occur inside Jaxl instance lifecycle. A list of available event callbacks with some explanation can be found here. For example, most of the XMPP applications will usually register a callback over on_auth_success event. As and when this event occurs inside Jaxl instance lifecycle, registered function will be callback’d with necessary parameters (if any).

Related Links

  • Read library documentation
  • Download the latest and greatest source from GitHub.
  • Have any Question? Want to discuss? Need Help? Use Google Group/Forum.
  • Found something missing or a bug in the source code? Kindly report an issue.
  • Fixed a bug? Want to submit a patch? Want to improve documentation? Checkout source code and contribute to the library

XMPP Application Examples

HTTP Application Examples

Stay Tuned
In coming weeks, under this series of blog posts titled “Working with Jaxl – A Networking Library in PHP”, I will cover following major topics with sample code:

  • Explanation of each Core stack class and how to use them
  • Design of each XMPP and HTTP stack class
  • XMPP over HTTP
  • XMPP File Transfer and Multimedia Sessions
  • Understanding and Using External Jabber Components
  • Asynchronous Job/Task Queues
  • Developing Concurrent and Parallel Systems

If you have any specific topic that you would like me to be cover, kindly let me know via your comments here.