VOIP integration with TIMP

I installed the demo version of TIMP and everything works except VOIP (Voice over IP) calls between TipicIM clients; I keep getting the following error message: "Timeout trying to contact Tipic Server Voip Plugin, please check your firewall rules (state 1)". I manage the LAN here and I have opened all ports.

--------------------------------------------------

In order for VOIP calls to work you need to do the following:
- enable s2s communication (when running the configuration Wizard)
- make sure that the name of the server (and the machine where TIMP is installed and gets its name) is a FQDN (Fully Qualified Domain Name.