(The first of a multi-part series on APIs for Asterisk, this article covers the current interfaces, their strengths and weaknesses. Check back in a few days for part two: a proposal for an enhanced, unified interface for Asterisk programming.)
At the AstriDevCon this year we talked about a number of aggressive projects to make significant improvements to the platform. At the top of the list were a rewrite of our SIP channel and better APIs for application development. Both efforts are important and, frankly, long overdue. I’ll leave the SIP efforts to others and concentrate on the APIs.
Asterisk currently includes a total of eight interfaces:
- The internal C language interfaces
- The Dialplan scripting language(s)
- The Asterisk Gateway Interface (AGI)
- The Asterisk Manager Interface (AMI)
- The External IVR interface / protocol
- The Asterisk Command Line Interface (CLI)
- The outgoing call file spool
- The Asterisk configuration files
These interfaces provide various means of interfacing with Asterisk. Unfortunately, they’re inconsistent, awkwardly structured, poorly documented and generally developer-unfriendly. Let’s take a look at the pros and cons of each.
The C API
Asterisk’s internal C API is used to write applications and functions which are then exposed to the Dialplan and other interfaces. On the positive side, the resulting apps are fast, have virtually no overhead and have access to all of the …
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About three weeks ago my company (Digium) launched AsteriskExchange, a marketplace of sorts for Asterisk add-ons and Asterisk-based solutions. The idea is to give users a single site that catalogs all the amazing products and projects that connect with Asterisk. Open source and free (as in no-strings-attached) products qualify for free listings, while commercial offerings pay a listing fee that helps cover the cost of maintaining and marketing AsteriskExchange.
One of the first open source projects to get listed is an absolutely fantastic collaboration and conferencing system called BigBlueButton. BigBlueButton (BBB) is similar in function to WebEx or GoToMeeting, but adds some really cool features including multi-presenter video, low-bandwidth document sharing and an open API for integration with other systems. The audio conferencing component of BBB is provided by Asterisk, which is one of fourteen open source “engine-level” components that power the system.
The BigBlueButton client is a browser-based Flash app, so there’s no software package to install or update. Unlike most other collaboration tools on the market, BBB works with Windows, Mac and Linux. The system was built for the distance learning market but works perfectly well as a collaboration or marketing tool for business. The package is licensed under a combination of the LGPL and the AGPL. The sponsoring company, Blindside Networks, offers installation, …
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