app.cabal

name:                app
version:             0.0.0.1
synopsis:            stuck
description:         stuck
license:             BSD3
license-file:        LICENSE
author:              Daisuke Fujimura
maintainer:          me@fujimuradaisuke.com
copyright:           (c) 2014 Daisuke Fujimura
category:            Web
build-type:          Simple
cabal-version:       >=1.8

Executable app
  main-is:
      Main.hs
  ghc-options:
      -Wall
  build-depends:
      base >= 4.0 && < 5.0
    , http-types
    , wai >= 3.0.0
    , wai-extra >= 3.0.0
    , warp

Main.hs

{-# LANGUAGE OverloadedStrings #-}
import Network.Wai
import Network.HTTP.Types
import Network.Wai.Handler.Warp (run)

app :: Application
app _ respond = do
    respond $ responseLBS
        status200
        [("Content-Type", "text/plain")]
        "Hello, Web!"

main :: IO ()
main = do
    run 8080 app