Interactive Screen Pops with Asterisk & XMPP

I’ve got a thing about screen pops.
I’ve written before about using Asterisk and XMPP to enable IM-based screen pops, but the recent release of Asterisk 1.8 creates a whole new reason to be excited about this topic.

The new version of Asterisk includes a new dialplan function called JABBER_RECEIVE.

This new function nicely compliments the existing JabberSend() dialplan application and lets you read incoming XMPP messages into dialplan variables (via Set()).

Now that you can both send and receive XMPP messages via the dialplan, it is possible to build sophisticated CTI applications using standards-based XMPP servers and clients with nothing but extensions.conf. Here’s how.

You’ll need an XMPP server with (at least) two accounts. One for you, as a user. One for Asterisk. You’ll also want to fire up your XMPP client and add the Asterisk user to your buddy list.

Set up jabber.conf with the details of the Asterisk account on your XMPP server (make sure you run jabber reload in the Asterisk CLI after modifying the file):

Once you’ve done that, you’ll need to add some dialplan logic to use both JabberSend() and JABBER_RECEIVE (run dialplan reload in the Asterisk CLI after adding this logic):

In this simple example, anytime a call comes into the default context, a set of IM messages are sent to the XMPP account (where represents the host name/IP for your XMPP server). The following line in the dialplan will cause Asterisk to wait 10 seconds to receive a response from

exten => _XXXX,n,Set(OPTION = ${JABBER_RECEIVE(asterisk,,10)})

When a response is received, it is read into the variable OPTION. Subsequent dialplan logic will either send the call to the extention that was dialed, or simply hang up (you could just as easily add options and logic to route the call to one of several different phone numbers or to voicemail).

That’s it!

This powerful new addition to Asterisk makes building sophisticated, interactive XMPP-based screen pops easy. Just imagine what other juicy little nuggets await in the new version of Asterisk.

Happy screen popping!

Building Voice Applications with Tropo and Node.js

I’ve been smitten of late with Node.js.

Node.js is a framework for building server-based applications in JavaScript. Node.js is event driven, so if you got a fairly good understanding of state-driven development frameworks you’ll probably get it quickly. If not, start here.
I wanted to learn more about Node.js, so I decided to build a module. There are lots of modules out there, but I wanted to do something very specific with mine. I wanted to use Node.js to build voice applications. (Not a shocker, it’s what I do.)

Turns out Node.js is a very nice match for the Tropo WebAPI, a cloud-based API for building sophisticated speech and communication applications. The Tropo WebAPI speaks JSON, and I can’t think of any more natural way of creating and consuming JSON than with good ‘ol JavaScript. Really, you can see why this gets me excited.

The Node.js module that I’ve been working on for interacting with the Tropo WebAPI is now available on GitHub. It comes with some very nice examples, and even a set of unit tests (yes, Virginia, you can write unit tests with Node.js). It has everything you need to get started using Node.js to write voice apps in JavaScript.

If you decide to give it a try (which I hope you do), there are some additional ingredients I would recommend adding to the mix:

  • The Express.js framework – a Node.js module very much like Sinatra in Ruby or Limonade in PHP.
  • CouchDB – The wonderfully powerful document-oriented storage engine that uses both JavaScript (for map/reduce and views) and JSON (for storing documents). There are also many fine Node.js modules available for interacting with CouchDB.

With these ingredients you’ve got a pretty powerful foundation on which to build robust, sophisticated multi-channel communication apps.

But why would you want to build a voice application with JavaScript?
Pretty much all of the voice application development tools and technologies that have been developed over the last decade or so have one essential unifying characteristic – each of them seeks to leverage easy to understand, low cost web technologies to build phone applications.

This principle can be seen very clearly in the approach embodied by the new Node.js library for the Tropo WebAPI. If you can write JavaScript, you can build sophisticated, cloud-based communication applications that not long ago required specialized skills, training, software and hardware (Big bucks, people. Big bucks).

Cloud-based telephony services based around simple to use APIs that employ widely supported standards like HTTP and JSON are democratizing phone and voice application development.

It’s really exciting to be a part of this trend and to contribute tools that others can use to build powerful applications.