Hi Arnaud, One thing you might want to try is to stop using the PortNumber data constructor, and instead rely on 'fromInteger' to do the right thing. The data constructor assumes that it's argument is in network byte order, which won't always be the case. It's not obvious that the constructor should be avoided - this is the second time today I've seen this! Take care, Antoine On Jun 3, 2010 5:13 PM, "Arnaud Bailly" wrote: Hello, I have the following code which works ok on Linux and Windows XP, but fails on Mac OS X with error message: Connect: does not exist (connection refused) The server: doStartstate = do pr <- liftIO $ runProcess ... liftIO $ threadDelay 500000 st <- get put st { slimHandle = Just pr } The client: fetchAnswers st msgs = liftIO $! do let port = PortNumber $ fromInteger $ port $ config st cnx <- connectTo "localhost" port Help most welcome, thanks Arnaud _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe