You have the basic infrastructure working, so now improve the clients so that most of the game works without anything fancy going on. Make sure that your server can handle at least 3 clients, but that should not be a limitation.
The clients also need to use asynchronous I/O if they are going to receive messages from the sub-server as well as from the terminal.
Turn in a script showing your server handling multiple clients, and the clients able to interact to make offers and bids.