Basic client/server

Client.hs

import Network
import System.IO
import Control.Exception

main = loop

loop :: IO a
loop = do
      putStr "Enter message: " >> hFlush stdout
      message <- getLine
      bracket (connectTo "localhost" $ PortNumber 9001)
              hClose
              (\h -> hPutStrLn h message)
      loop

Server.hs

import Control.Concurrent
import Control.Exception
import Network
import System.IO



main :: IO ()
main = do
      putStrLn "Opening socket on port 9001"
      bracket (listenOn $ PortNumber 9001) sClose loop



-- | Listens on a socket and forks a worker thread for incoming connections
loop :: Socket -> IO ()
loop socket = do
      (h, _, _) <- accept socket
      forkIO $ worker h
      loop socket



-- | Prints received messages
worker :: Handle -> IO ()
worker h = (`finally` hClose h) $ do
      message <- hGetLine h
      putStrLn $ "Received message: " ++ message