I'm trying to get started on an instant messaging/VoIP project that uses a client-server architecture, and I'm thinking of looking at open source projects such as Jabber to understand the underlying architecture. I've had a bit of network programming experience more than a decade ago but haven't done it since (more of a firmware programmer the past few years).
The end goal is to have a full featured server setup to handle IM/VoIP and mobile clients (Android/iOS/etc) that supports secure calls/IMs, groups, and other cool stuff, but I'll start with a basic IM infrastructure (server-client) first.
Does anyone have any recommendations of which open source project I should start looking at first, as well as any relevant tutorials/guides/forums for IM/VoIP development? I'm looking at ejabberd for the server side as it uses XMPP standards and has Windows/*NIX/OSX support, but it uses erlang which I'm not familiar with (I speak C/C++ and some Java)