network-simple-0.2.0.0: examples/echo-tcp.hs

{-# LANGUAGE OverloadedStrings #-}

-- This is an example TCP server that listens on port 9000 and echoes
-- back to clients whatever they send. Incoming connections and handled
-- concurrently.

module Main (main) where

import           Control.Concurrent (forkIO)
import           Control.Monad
import qualified Data.ByteString.Char8 as B
import qualified Network.Simple.TCP as T
import           Network.Socket.ByteString (recv, sendAll)


main :: IO ()
main = do
    T.listen "*" "9000" $ \(lsock, laddr) -> do
      putStrLn $ "Listening for TCP connections at " ++ show laddr
      forever . T.acceptFork lsock $ \(csock, caddr) -> do
        putStrLn $ "Accepted incoming connection from " ++ show caddr
        echoloop csock

  where
    echoloop sock = do
      bs <- recv sock 4096
      when (not (B.null bs)) $ do
        sendAll sock bs
        echoloop sock