Sample telnet chat in Haskell

gistfile1.hs

module Main(main) where

import Network
import System.IO
import Control.Monad
import Control.Concurrent
import Data.List

type Message = String

data ChatUser = ChatUser { userId :: Int, username :: String }
        deriving Eq

data ChatMessage = ChatMessage { messageFrom :: ChatUser, messageText :: Message }
                 | QuitMessage { messageFrom :: ChatUser, messageText :: Message }
                 | JoinMessage { messageFrom :: ChatUser }

instance Show ChatUser where
        show (ChatUser uid name) = name ++ "(" ++ show uid ++ ")"

instance Show ChatMessage where
        show (ChatMessage user message) = show user ++ ": " ++ message 
        show (QuitMessage user message)
                | null message = "! " ++ show user ++ " saiu."
                | otherwise    = "! " ++ show user ++ " saiu: " ++ message
        show (JoinMessage user) = "! " ++ show user ++ " entrou."

port :: PortID
port = PortNumber 23

main :: IO ()
main = withSocketsDo $ do
        let userCount = 0
        chan <- newChan
        socket <- listenOn port
        handleConnections socket userCount chan

handleConnections :: Socket -> Int -> Chan ChatMessage -> IO ()
handleConnections socket userCount chan = do
        (socketHandle, _, _) <- accept socket
        hSetBuffering socketHandle NoBuffering
        let nextUserNumber = (userCount + 1)
        _ <- forkIO $ handleUserConnection chan socketHandle nextUserNumber
        handleConnections socket nextUserNumber chan

handleUserConnection :: Chan ChatMessage -> Handle -> Int -> IO ()
handleUserConnection chan socketHandle thisUserNumber = do
        name <- readUsername socketHandle
        let thisUser = ChatUser thisUserNumber name
        broadcast chan $ JoinMessage thisUser
        chanReader <- dupChan chan
        readerThread <- forkIO (startReader chanReader socketHandle thisUser)
        quitMessage <- (startSender chan socketHandle thisUser) 
                            `catch` (\_ -> return "")
        broadcast chan $ QuitMessage thisUser quitMessage
        killThread readerThread
        hClose socketHandle

readUsername :: Handle -> IO String
readUsername socketHandle = do
        hPutStr socketHandle "Informe seu nome: "
        readLine $ socketHandle 

startReader :: Chan ChatMessage -> Handle -> ChatUser -> IO ()
startReader chanReader socketHandle thisUser = forever $ do
        message <- readChan chanReader
        when ((messageFrom message) /= thisUser) (display message socketHandle)

startSender :: Chan ChatMessage -> Handle -> ChatUser -> IO String
startSender chan socketHandle thisUser = do
        line <- readLine socketHandle
        if "/quit" `isPrefixOf` line
          then return . dropWhile (== ' ') $ drop 5 line
          else do
            broadcast chan (ChatMessage thisUser line)
            startSender chan socketHandle thisUser

broadcast :: Chan ChatMessage -> ChatMessage -> IO ()
broadcast = writeChan

display :: ChatMessage -> Handle -> IO ()
display message socketHandle = do
        hPutStr socketHandle (show message ++ "\r\n")
        hFlush socketHandle

readLine :: Handle -> IO String
readLine = liftM (filter (/= '\r')) . hGetLine

Olá, gostei do código, mas como eu testo isso?? Eu e a outra pessoa em outro computador temos que ter o ghci para interpretar e carregar oss módulos de Haskell, e como envio e leio? Obrigada!