chat.hs

module Main where

import Network.Socket
import System.Environment
import Control.Concurrent
import Control.Monad

-- Port number to listen on
listenPort :: PortNumber
listenPort = 3000

-- | The main function
main :: IO ()
main = withSocketsDo $ do
    args <- getArgs -- get arguments
    (host,port) <- parseArgs args -- parse arguments
    s <- setupSocket -- setup our socket

    -- Make the remote address we're talking to
    let remote = SockAddrInet port host

    -- Make a new thread to read messages from the socket
    read_t <- forkIO $ readChat s

    -- Continue in this thread and write messages to the socket
    writeChat s remote

-- | A function to parse arguments
parseArgs :: [String] -> IO (HostAddress, PortNumber)
parseArgs (h:p:_) = do
    host <- inet_addr h
    return (host, port)
    where
        port = fromIntegral . read $ p

-- | A function to create the socket
setupSocket :: IO Socket
setupSocket = do
    -- UDP socket
    s <- socket AF_INET Datagram defaultProtocol
    bindSocket s (SockAddrInet listenPort 0)
    return s

-- | A function to read messages from the socket and print them
readChat :: Socket -> IO ()
readChat s = forever $ do
    (s,l,f) <- recvFrom s 4000
    putStrLn $ (show f) ++ " (" ++ (show l) ++ ") >>> " ++ s

-- | A function to read messages from stdin and send them to the remote host
writeChat :: Socket -> SockAddr -> IO ()
writeChat s a = forever $ do
    msg  <- getLine
    sendTo s msg a
    putStrLn $ "Sent to " ++ (show a)