SME Server - Teamspeak

I have recently installed SME server on an older pc to play with. I
installed Teamspeak server on it and it works fine on my internal
network. I allowed udp port 8767 passthrough to this server on my
router, however the teamspeak server will only allow connections from
pc's on my internal network. Is this maybe a limitation of this version
of linux? Is there some setting somewhere i haven't seen to allow
external ip addresses to connect to the linux machine? I am somewhat
new to linux. Any help would be appreciated

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