the problem, I can not create a server UBUNTU

[MPx]

well, if you don't port forward, ofc you can still connect to your server but will be considered as a LAN server.

Try this, open a terminal and type:

[SELECT ALL] Code:

iptables -A FORWARD -p UDP --dport 28763 -j ACCEPT
iptables -A FORWARD -p UDP --dport 28764 -j ACCEPT

for a port of choice:

[SELECT ALL] Code:

iptables -A FORWARD -p UDP --dport 8888 -j ACCEPT