Question

I start the executable (after building it with cabal) and it says “Application launched, listening on port 3000.” Next I connect to it with my web browser and the console says “threadWaitRead requires -threaded on Windows, or use System.IO.hWaitForInput.” The web browser never connects. Not sure what this is actually recommending I do to resolve the problem.

{-# LANGUAGE TypeFamilies, QuasiQuotes, MultiParamTypeClasses,
             TemplateHaskell, OverloadedStrings #-}
import Yesod

data HelloWorld = HelloWorld

mkYesod "HelloWorld" [parseRoutes|
/ HomeR GET
|]

instance Yesod HelloWorld

getHomeR :: Handler RepHtml
getHomeR = defaultLayout [whamlet|Hello World!|]

main :: IO ()
main = warpDebug 3000 HelloWorld

Answer 1

I’m not sure how you’re compiling the executable, but using -threaded sounds like it would solve the problem, e.g.:

ghc --make hello-yesod.hs -threaded
hello-yesod.exe