How to open Port 9987 for a TeamSpeak 3 Server?

Umm so I’m currently using the Comodo Firewall with Proactive Defense on a home computer that I only use to run my TeamSpeak 2 Server through the port 8767. No problems with that.

However, TeamSpeak 3 recently got released and I installed the new TeamSpeak 3 Server on it. The server is working. I’m able to connect to my own server through my own home network using port 9987, even though I had to manually allow my laptop to connect to the computer I use to run the server. On the other hand, people from the internet are unable to join it. It appears that the firewall is somehow blocking the ftp clients from accessing the server.

So pretty much what I want to do is open the port 9987 for ftp access. And my question is how do I do it?