Use the firewall links and open ports for UDP traffic
You will not regret it :)

Google hangouts:
The connection methods are attempted in this preferenced order:
A UDP connection from the participant to Google on ports 19305 through 19309
A TCP connection from the participant to Google on ports 19305 through 19309
A TCP connection from the participant to Google on port 80
A TCP connection from the participant to Google on port 443 (SSL)

Skype: Go to advanced settings and define a port, enable uPNP for it to open its own ports

ichat: who uses it? ;)