Official forums for BZFlag.org

What is it and how do I turn it on?

Google.com is your friend.

So is the forum search.

UDP is a connection-less protocol that is useful for sending time critical data, since if it doesn't get there, it doesn't resend the data. You don't "turn it on" in BZFlag, as it cannot be turned off. The reason you're getting kicked for not using UDP is either a poor connection, or a problem with your router. What brand of router do you have?

In a nutshell, there are two types of internet protocols, TCP and UDP. In TCP, a connection must be established between two computers, much like a telephone call. UDP, however, does not establish a connection, it just sends a message, much like a mail letter.

Because UDP is connectionless, it makes it easy to spam computers, since a connection does not need to be established, and this makes it difficult to track. For that reason, most routers block all UDP messages. The only way to access the program is to either open the UDP port on your router, or disable NAT (both of which aren't fun to do and could blow up any Windoze systems accessing the network).