Architecture : Connections

User / Client

Each User may do whatever they wish.

I.E. a bridge program might allow you to take part in multiple tournaments.

Each Client may be connected to by multiple Users

I.E. A bridge program and a poker program on the user's machine might both share the same fairdice client app.

Client / Server

Each Client may connect to multiple Servers

(multiple servers per user too).

Each Server may be connected to by multiple Clients

Indeed this has to happen for multi-user games.

Server / Host

Each Server may connect to or be connected to by multiple Hosts

For instance, a casino might run blackjack, roulette and poker hosts from the same server app.

Each Host may do whatever they want.

There is nothing to stop the creation of multi-host games on a peer-peer basis.

What you don't get is User / Server or Client / Host.

User / Host communication is likely to happen, either direct or through tunneling. However what is said between these is use-dependant and outside this specification.