import Control.Concurrent
import Network

import System.IO

main :: IO ()
main = withSocketsDo $ do
    m <- newEmptyMVar

    forkIO (waitAndPong m)
    ping m

-- The basic server
waitAndPong :: MVar () -> IO ()
waitAndPong m = do

    socket <- listenOn (PortNumber 8000)
    putMVar m ()
    (handle,_,_) <- accept socket
    hSetBuffering handle LineBuffering

    incoming <- hGetLine handle
    putStrLn ("> " ++ incoming)
    hPutStrLn handle "pong"


-- The basic client
ping :: MVar () -> IO ()
ping m = do
    _ <- takeMVar m
    handle <- connectTo "localhost" (PortNumber 8000)


    hSetBuffering handle LineBuffering
    hPutStrLn handle "ping"
    incoming <- hGetLine handle
    putStrLn ("< " ++ incoming)