VoIP and SIP, where to begin [closed]

Question

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 am 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.

Answer 1

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.

Answer 2

You could start with w3c's voice browser standards and the IETF SIP working group.