How to get ServerSocket to tell client that it's not accepting?

Question

I've had a couple of other topics recently, concerning my attempt to write a client/server TicTacToe game for my final project in Data Comm. I've got almost all of what I want worked out this week, but I'm stumped on this one. The project spec includes some way of controlling access to the application on the server -- do some work on figuring out the limits of the resources, and set up a way to limit the number of clients that can connect at one time.
I thought that for my purposes, for proof of concept, I would set it up so that up to 3 clients could play at one time, and up to 2 could be allowed to "connect, but wait for a turn" until someone playing logged off. Conceptually I can draw a flow chart of it, but what I can't figure is this -- I have a server object that accepts connections with ServerSocket.accept(), and sends off the socket created as an argument to a new thread of the ServerGame class. ServerGame has a static int for threadcount. I can code in ServerGame to limit it to 3 who can actively be allowed to play, and send a message back to someone who connects later to say, "Wait", and in the Server itself I can refuse to accept() if a 6th client tries to connect, but for that 6th client -- how can I get a message saying "You can't even connect now -- no room even in the queue"? If the server doesn't even accept(), what's the means of response, other than the poor client sitting there with an unresponsive button in his GUI? That's what happens now -- the first client that tries to connect when the server won't accept, his GUI just freezes. Not a good interface.
Unfortunately this is a Data Comm class, and the teacher is new this year and comes from 25 years in industry and knows C/C++, but no java.

Answer 1

My puzzlement is that I'm a beginner ( we just got introduced to the idea of sockets in class a month ago, and I chose java not only because I like it best but golly, the socket API in C and C++ is awful compared to java).
My understanding of ServerSocket is that it does not make a connection that it can use itself, but passes off to something or someone. My model is to have a ServerGame class, threaded so the Server spawns a new thread of ServerGame for each new socket and passes the socket to the constructor of the new ServerGame thread. The it goes off and does its thing.
So I don't understand what you mean by setting a flag (I understand flags, just not what the idea is in this case). And how can I call a function on a server on a different machine? Chicken and egg -- how can I communicate if I can't connect, and if I do connect the connection is sent off to the ServerGame, not the Server itself.
Wait -- just thought of something -- is this what you mean? If I set a condition that recognizes I've reached the limit, ServerSocket could create a connection but NOT send it to the ServerGame, but to a temporary object of some kind, that just sends back a message and closes and dies?
Sounds do-able, but time's up, I gotta get to school. I'll check in later
Thanks a lot
F