-- Echo server program

module Main where

import Control.Monad (unless)

import Network.Socket hiding (recv)

import qualified Data.ByteString as S

import Network.Socket.ByteString (recv, sendAll)

main :: IO ()

main = withSocketsDo $

    do addrinfos <- getAddrInfo

                    (Just (defaultHints {addrFlags = [AI_PASSIVE]}))

                    Nothing (Just "3000")

       let serveraddr = head addrinfos

       sock <- socket (addrFamily serveraddr) Stream defaultProtocol

       bind sock (addrAddress serveraddr)

       listen sock 1

       (conn, _) <- accept sock

       talk conn

       close conn

       close sock

    where

      talk :: Socket -> IO ()

      talk conn =

          do msg <- recv conn 1024

             unless (S.null msg) $ sendAll conn msg >> talk conn