TCP vs UDP

[Roberto Ramsis]

hello
thanks to everyone who replied to my last msg
what's the difference between a port TCP and UDP?
i am talking from a firewall concept,i want to know ,if i need to block a port,when should i block TCP and when UDP and when both?
Thanks in advance

_________________________________________________________________
MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*. http://join.msn.com/?page=features/virus