VoIP (Voice over IP) has recently gained in popularity as a less expensive alternative to traditional telephone systems, allowing free PC-to-PC calls and with many providers offering cheap connections for PC-to-telephone calls. Many companies are also finding VoIP systems to be a less expensive and more full-featured alternative to traditional PBX systems. But VoIP offers more than just a cheaper alternative to traditional telephone/PBX systems; the integration of voice communication with standard computer systems and networks allows for an unprecedented level of control of and interaction with telephony using standard software. Asterisk is an open-source PBX system, utilizing both VoIP and, optionally, hardware for connecting to traditional telephone systems. It runs on Linux, BSD, and Mac OS X, and supports multiple protocols and codecs, including SIP and H.323. In addition to providing all the features of a PBX and many other features, such as interactive voice response, it has one capability of particular interest to us: the ability to interact with external software--including, of course, Java--through a socket interface. We will take a brief look at VoIP in general, Asterisk in particular, and at the Asterisk-Java Library, which provides an easy way to interact with Asterisk using Java.

Michael Plezbert has been developing software for over 20 years, since the tender age of 12, using more languages and platforms over the years than he can remember. He currently works for Agilis Systems, developing software in a variety of languages for diverse platforms, from the latest in web technology to the latest mobile phones and devices. He also teaches in the CSE department at Washington University as an adjunct faculty member. He has a B.S. in Physics from Missouri State University and an M.S. in Computer Science from Washington University.