TCP UDP

I'm currently developing classes to handle TCP and UDP transmission in C#. I got it working in a LAN environment and I understand how to get it to work in a WAN environment. What I would like to know (if anyone could help me here), is at a high level, how does video games transmit packets back and fourth? I know that there is whats called a "master" server that clients connect to, to receive available games and join them (via TCP protocol). Then once the player joins the game, data is transmitted from the client to the master, then from the master to the host and other individual clients that are in the game (via UDP protocol). What I'm thinking is that there is practically always a stream of udp packets being sent and received throughout the game. With those packets containing player object positioning, rate of movement, etc, etc. The master server has to be setup to allow incoming requests and so does any computer that is hosting a game for everyone. So correct me if I am wrong here or add any suggestions.

Thanks!