I'm running pfSense 2.4.4... so yes, it's a firewall.
The article lists the following ports:
Allow Outgoing:
TCP Ports: 6800, 5222, 5223
UDP Ports: 5060, 5061, 10000 to 11000, 16600 to 16998, 19305
Allow Incoming on UDP Port: 10000
I'm hoping someone from OBi can actually provide updated technical requirements
so I don't have to sniff the traffic.