Hi
Recently, a client has asked me to do a custom application to manage intercoms. (Barix Annuncicom) After reading the documentation I can do most of the "managing" part, however I'm stuck with the VoIP part.
Are there any documentation, guides, articles, that will help me better understand and code a simple VoIP application? I am looking for a article that has little expectation of previous knowledge.
voip-info.org, is a nice resource guide if you wanna learn about VoIP platforms and protocols, is mostly open-source oriented and you'll find good articles there.
You could start with w3c's voice browser standards and the IETF SIP working group.
This reasonably high-level tutorial has lots of information, including common VOIP questions and a discussion of SIP functions, and book recommendations.
There are more specific tutorials dealing with introductory software implementations (e.g. using Asterisk) on the SWIK site.
If you want to find details on SIP, one of the best resources is Tech Invite.
Other very useful tool is SIPP which is SIP packets emulator with easy biult in XML scripting language which allows you to test different scenarios.