Since text can be sent from client to client, it is
*possible* to make a multiplayer game. However, without some type
of centralized, server-side processing of this information, it will
be incredibly easy for client programs to be hacked and cheating to
occur. I fully understand the power of UDP traffic between clients,
but without server checks and balances of certain information
(collision detection, trusted information, etc), that power is
overwhelmed with the possibility of hacking.
Is there any mechanism now, or will there be any in the near
future, that will allow server logic to process *some* messaging
Today, you can use currently-shipping FMS with RTMP for
server-based communication, and RTMFP with Stratus for
client-to-client communications. There's nothing stopping you from
having multiple NetConnections in your SWF.
Alternatively, you could use a web service, or XML sockets to
a server, or something like that for server-based communications.
Farther down the road, a future version of Flash Media Server
will support RTMFP, but no release plans have been announced yet.