How to open TCP and UDP Ports in the System Firewall
If the Virola server is not accessible from the outside, you may need to open the TCP and UDP ports in the system firewall settings. The TCP port is used for text messaging, file transfer, etc. The UDP port is used voice chats.
On Fedora Linux
sudo firewall-cmd --add-port PORT/tcp --add-port PORT/udp --permanent
sudo reboot