Bidi sockets should work now with the recent winsocket/sdlsocket patch I put in right before u1. You create the socket with the FILE_CREATE flag set and it'll create a server-type socket waiting for something to connect (telnet should work in a pinch), after which it should work bidirectionally. (Creating a socket without FILE_CREATE should result in bidi also, but of course you need some kind of server at the other end to connect to).
I think PTY was always bidi but I'm not sure how to test it
