Networking sample in Haskell

import Network.Socket import Network.BSD import System.IO (Handle, IOMode(ReadWriteMode), hPutStrLn, hGetLine, hClose) import Control.Monad (liftM) import Control.Concurrent (forkIO) import Control.Exception (finally) connectTo :: String -> Int -> IO Handle connectTo host port_ = do let port = toEnum port_ sock <- socket AF_INET Stream 0 addrs <- liftM hostAddresses $ getHostByName host if null addrs then error $ "no such host : " ++ host else return () connect sock $ SockAddrInet port (head addrs) handle <- socketToHandle sock ReadWriteMode return handle listenAt :: Int -> (Handle -> IO ()) -> IO () listenAt port_ f = do let port = toEnum port_ lsock <- socket AF_INET Stream 0 bindSocket lsock $ SockAddrInet port iNADDR_ANY listen lsock sOMAXCONN loop lsock `finally` sClose lsock where loop lsock = do (sock,SockAddrInet _ _) <- accept lsock handle <- socketToHandle sock ReadWriteMode f handle loop lsock server = withSocketsDo $ do listenAt 12345 (\h -> forkIO (do putStrLn "connection." hPutStrLn h "Hello, and Goodbye!" `finally` hClose h) >> return ()) client = withSocketsDo $ do h <- connectTo "localhost" 12345 hGetLine h >>= putStrLn hClose h