There are many options for making SIP/VoIP phone calls over the Internet. There are some with nice user interface, some that get you over almost all the the little hurdles and problems (like for example X-Lite, which you should try if you're ever stuck unable to make a connection, as it seems to work around most problems on its own). But if you're a real geek at heart, there is only one choice: pjsua. pjsua does not have any such timewasting features as a GUI or an address book.

Read the Full Article Here