11.4.2.1. Server Side

First of all, you need a provider offering the service. This service might integrate traditional telephony and it might or might not be free. Among others are SIPphone, Vonage, Lingo, AOL TotalTalk and many locally accessible providers offering the so-called "full phone service". Internet phone service only is offered by Skype, SIP Broker, Google and many others.

If you want to set up a server of your own, you might want to look into Asterisk.