[Slice]

You could just use iptables and do something like:

Code:

#Whitelist
-A INPUT -p all --dport 7777 -s 1.2.3.4 -j ACCEPT
-A INPUT -p all --dport 7777 -s 5.6.7.8 -j ACCEPT

# When you do DROP the server will appear completely dead
-A INPUT -p all --dport 7777 -j DROP