{-# LANGUAGE OverloadedStrings #-}
-- A simple example of an epoll based http server in Haskell.
--
-- Uses two libraries:
--   * network-bytestring, bytestring-based socket IO.
--      - cabal install network-bytestring: 
--
--   * haskell-event, epoll-based scalable IO events
--      - git clone git://github.com/tibbe/event.git
--      - autoreconf ; then cabal install
import Network hiding (accept)
import Network.Socket (fdSocket, accept)
import Network.Socket.ByteString
import Data.ByteString.Char8
import System.Event
import System.Posix
import System.Posix.IO
main = withSocketsDo $ do
    sock <- listenOn $ PortNumber 5002
    let fd = fromIntegral (fdSocket sock)
    mgr <- new
    registerFd mgr (client sock) fd evtRead
    loop mgr
client sock _ _ = do
    (c,_) <- accept sock
    sendAll c msg
    sClose c
msg = "HTTP/1.0 200 OK\r\nContent-Length: 5\r\n\r\nPong!\r\n"

btnz@vmubuntuserver:~/work/code/echo-server-event-model$ cat Main.hs

module Main where

import Network.Socket

import Network.Socket.ByteString (recv, sendAll)

import GHC.Event as Event

import qualified Control.Exception as E (bracket)

import Data.ByteString.Internal (packChars)

hints = defaultHints {addrFlags = [AI_PASSIVE], addrSocketType = Stream}

msg = "HTTP/1.0 200 OK\r\nContent-Length: 5\r\n\r\nPong!\r\n"

main :: IO ()

main = do

putStrLn "Hello, Haskell!"

addr <- head <$> getAddrInfo (Just hints) Nothing (Just "3000")

E.bracket (sock addr) close eventServer

return ()

where

sock addr = do

s <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)

setSocketOption s ReuseAddr 1

withFdSocket s setCloseOnExecIfNeeded

bind s $ addrAddress addr

listen s 1024

return s

eventServer s = do

fd <- withFdSocket s (\ci -> return (fromIntegral ci))

mgr <- Event.new

Event.registerFd mgr (service s) fd Event.evtRead Event.OneShot

-- loop mgr

service :: Socket -> FdKey -> Event -> IO ()

service s _ _ = do

(c, _) <- accept s

sendAll c $ packChars msg

close c