If you have a site running on port 80. Your only way to block clients from connnecting is to restrict access by IP's or simply don't offer that service.
There are various other ways to check is port X responding to connections so i don't get why in earth you would like to block only telnet since it uses the very same TCP protocal than any other software connecting to port X.
Last edited by GameFrame; 05-05-2011 at 02:52 PM.
█ NiX API - A powerful Anti-Proxy/Anti-Fraud and IP Reputation Lookup API