The ability to listen on ports is a new feature in AIR 2 that should be out soon, but is currently in beta. If you are using version 2, you can create an HTTP server if you want. A general example of building a socket server can be found here .
Note that AIR applications are event driven, not streaming. Of course, you can deal with several connections, so I assume that the environment itself launches them in different threads, but the code you write is not related to streaming or blocking, you just register for connection events, data, etc. d. And process them. (This may be what you mean by psuedo-threaded, I don't really do such things.)
However, there is a very big caveat for this, which AIR does not currently recommend Adobe for dumb server applications. As far as I understand, there may be times when the runtime opened a confirmation dialog box, and some things about the application may not work correctly until you retire to the server to reject the dialog.