forkIO implemenation

I infer from a discussion from March 2002 that concurrency in Haskell is not implemented in native threads, at least in Windows. Is this true? The discussion also implies that an implementation is in the works. The reason I ask is that when I forkIO and accept from a socket in the new thread everything seems blocked. Is this the expected behavior? It would be really nice to be able to listen on multiple sockets in a single process. Thanks, Jason Feingold