[Haskell-cafe] How to make asynchronous I/O composable and safe?

[Joey Adams]

I uploaded a package that creates an STM layer over a network connection:

    http://hackage.haskell.org/package/stm-channelize

I haven't used it in anger yet, but I hope it's a step in the right
direction.  I included a sample chat client and server.  The client is
pretty cute:

    main =
        let connect = connectTo "localhost" (PortNumber 1234) >>= connectHandle
         in channelize connect      $ \conn ->
            channelize connectStdio $ \stdio ->
                forever $ atomically $
                    (recv conn >>= send stdio) `orElse`
                    (recv stdio >>= send conn)

I use channelize on both the network connection, and on stdin/stdout.

The server is much longer, but shouldn't be terribly confusing.  It
demonstrates kicking out a client without a dangerous asynchronous
exception, something we can't do easily without waiting on
alternatives (i.e. orElse).

-Joey