If more than MAX_CLIENT connections, put further connections into a queue. Notify queued connections how many clients are ahead of them in the queue every few seconds. Once a connected client disconnects, connect the first client in the queue.
I've decided to do this on a per-server basis, not per scene. This has the unfortunate side effect of putting people back in the queue when they move from one scene to the next if the server is heavily loaded.
If more than MAX_CLIENT connections, put further connections into a queue. Notify queued connections how many clients are ahead of them in the queue every few seconds. Once a connected client disconnects, connect the first client in the queue.