On line 29, instead of liftIO $ do mapM_ ... runResourceT $ do ... ... why not liftIO $ mapM_ ... ... ... ? Regarding threads, you should use resourceForkIO [1] which has a quite nicer interface. So you telnet would end like: telnet :: String -> Int -> IO () telnet host port = runResourceT $ do (releaseSock, hsock) <- with (connectTo host $ PortNumber $ fromIntegral port) hClose liftIO $ mapM_ (\h -> hSetBuffering h LineBuffering) [ stdin, stdout, hsock ] resourceForkIO $ sourceHandle stdin $$ sinkHandle hsock sourceHandle hsock $$ sinkHandle stdout release releaseSock Disclaimer: code not tested =). Cheers, [1] http://hackage.haskell.org/packages/archive/conduit/0.0.2/doc/html/Control-M... -- Felipe.