Large Scale Chat Program

[Tron86]

I am somewhat new to Winsock and Async Socket Connections. I have been working on a chat program that has more features then just talking in a chat room. I would love for this program to be able to handle 100-200 users or more if need be. Users can create rooms inside the chat lobby, and have their own friends list. The problem I see with all of this is how I handle commands. I am looking for input/suggestions on what my limitations might be, or ways to improve this system. I have been storing some data on a MySQL database, so I am able to offload some stress, I guess. I worry also about putting too much strain on MySQL.

Currently the server handles all interactions between clients, nothing is "P2P". For instance when a user connects, he sends a string with a command (IE "|Conn|Username" and this is received by the server, and then sent out to all the clients from which they take the necessary action. When they create a room something similar, or if they need information about a user. There are a lot of other commands, but most do not get sent to all clients. My worry is, when 200 people are on it, and all sending information/creating rooms/sending messages(IM) to friends the amount of data Winsock has to process is going to cause lag. Now I know there will be a limitation at some point. But are there better ways to handle this? Any suggestions?