10-09-2011 18:42 - edited 02-07-2012 20:35
This guide will concentrate on the open SIP standard based VoIP, because S40 does not have Java APIs to build closed system VoIP solutions (such as Skype, Fring, Nimbuzz ...)
Nokia maintains a list of the S40 phones that have built in SIP VoIP capability in the firmware.
Configuring the phone for VoIP usage
There are three different ways how to configure VoIP in use in S40,
There exists a free tool for the manual configuration called n0kVoIP which makes the process easier.