Can someone please direct me to an example like this. I have to use UDP because tcp is slow at sending packets. And I'm not too sure on how to use udp.

I know it needs no connection but I've just been having problems sending data to the right computers.. I can't explain. can someone show me an example of like a chat that uses multiuser udp. Like I only need to send data to one person for things like private messaging and it seems udp is sending the data to all persons..

please help
thanks