Haskell websockets - standalone

SimpleWebsockets.hs

{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeApplications #-}

import           Protolude hiding (finally)
import           Control.Exception.Safe (finally)
import qualified Network.WebSockets as Ws

main :: IO ()
main = do
  -- Start the websocket server
  Ws.runServer "127.0.0.1" 8080 $ wsApp

  where
    wsApp pending = do
      conn <- Ws.acceptRequest pending
      Ws.withPingThread conn 30 pass $ do
        -- Send message on connect
        Ws.sendTextData @Text conn "connected"

        -- Run web socked API in an infinite loop
        -- Call disconnectWs when done
        flip finally disconnectWs . forever $ do
          -- Get text data
          msg <- Ws.receiveData @Text conn
          -- Write text data
          Ws.sendTextData @Text conn $ "echo: " <> msg

    disconnectWs =
      pass