[SDL] Good multiplayer game design?

[Leo M. Cabrera]

Yeah, alright, so all I'll send is 33 bytes, the rotation, x/y axes, 
name, and team flag. (I'll have to send some more data later on, such as 
being on a vehicle or not, weapon, etc... :-P)
But, how do I make it only send data when it has changed? Do I make the 
client send a boolean flag before anything else, and if it's false, then 
quit receiving data from that user and go to the next one? Thanks you 
all! ;-)