Actually, if you combine network with network-run then it is the right level of abstraction:

{- cabal:
build-depends: base, network, network-run, monad-loops
-}

import Network.Run.TCP
import Network.Socket
import System.IO
import Control.Monad.Loops

main = runTCPServer (Just "127.0.0.1") "9999" talk where
  talk s = do
    h <- socketToHandle s ReadWriteMode
    l <- hGetLine h
    case words l of
      ["GET", resource, "HTTP/1.1"] -> do
        whileM_ (("\r" /=) <$> hGetLine h) (pure ())
        let path = concat
              [ "htdocs/"
              , dropWhile (== '/') resource
              , if last resource == '/' then "index.html" else ""
              ]
        hPutStr h "HTTP/1.1 200 OK\r\n\r\n"
        hPutStr h =<< readFile path
        hClose h
      _ -> error "todo"