Setting up a VOIP system through web interface

Hi VoIPers,

I am trying to setup a single server that people can connect and speak to each other from different location.
Basically need some suggestion or guide what/how to set it up as I am bit stuck.

Simply, architecture is as described below:
User A puts on a headset with Microphone that is connected to a PC_A.
User B puts on a headset with Microphone that is connected to a PC_B.
They go to a website which is a webserver that I am going to run.
They login using their username and password which might have different access.
They have function of calling online people who is logged into the website.
A calls B, B answers the call and they communicate over normal headset.

All calls has to go through digitally. Nothing goes through analog signal. which will reduce the cost of national/international call charges(don't want to use PRI nor analog line).

Simple as recording a voice using some software and sending it through to destination. They listen to it. But this just needs to run in a real time.

So my questions are:
1. Is there a good open source that can help me getting this done? (Not sure Asterix, Jabber, or some open source like this might help.)

2. What programming language should I be using to build a website/server. (Possibly Active-X control can be installed on client's PC which will install the part of interface run on their PC. But preferred to have this solution run on a Server-sided only for a start.)

3. Does this uses VoIP at all? I am still new to VoIP.


I just don't know where to start... I have created a webserver at home for testing and trying to build a website that can be a front end of customers and administrator. (Customer will have such a function of calling people login in and access forum etc. Admin will have function of tracking the record of calls and manage users/forum).

Thanks in advanced.