After reading several webpages about networking, in attempt to trying to understand basic networking, (I've never done networking before) I've made a few classes that is designed to make somewhat of a simple chat room. The following classes will be posted below:

ChatServer: <http://paste.strictfp.com/32591> ((Edited recently)Creating the actual server that waits for people to connect to it, in this case, through port 9045)

ChatSession: <http://paste.strictfp.com/32583> (When a client is found, from the server code above, it creates a new session, which just basically reads the messages that are sent by the clients)

ChatClient: <http://paste.strictfp.com/32584> (Allows a client to write to the server)

ServerRunner: <http://paste.strictfp.com/32585> (Main method for running the server)

ClientRunner: <http://paste.strictfp.com/32586> (Main method for running a client, which connects to the server)

I know the code above isn't the best, considering the fact that I didn't add any checks to see if the socket/client got disconnected, or something got interrupted. But then again, this was just a practice in order to help me try and grasp the concept of networking.

So these 5 classes together work fine, but I have a question/concern that would be very much appreciated if answered:

How do I send a message from the server to a client?

The reason why I'm asking is this because I want to make a simple multiplayer tic-tac-toe game, in which there will be a server, and 2 clients (both representing players) and basically what I had in mind was that whenever the clients click on buttons, I'd send a message to the server. And then I would send the message back to both clients in order to modify both of their games. And I'm just a little confused about how it works, due to my lack of networking knowledge. I'd appreciate if you didn't redirect me to another URL, unless very very very simple, because I prefer if people explain it to me in simplest terms. If someone can help me, it'd be very much appreciated.