Unexpected Connection Close

connection_close.hs

module Main where

import qualified Data.Text as T
import qualified Network.WebSockets as WS
import qualified Control.Concurrent as C
import qualified Control.Monad as M


main :: IO ()
main = do
  WS.runServer "0.0.0.0" 9160 acceptConnection

acceptConnection pending = do
  conn <- WS.acceptRequest pending
  WS.forkPingThread conn 30
  bucket <- C.newMVar conn
  C.forkIO $ sendPing bucket
  return ()

sendPing bucket = do
  C.threadDelay 100000
  connection <- C.readMVar bucket
  WS.sendTextData connection $ T.pack "HI"

test.html

<script type="text/javascript">
  var connection = new WebSocket("ws://localhost:9160/?worldID=123");
  var secondConnection = new WebSocket("ws://localhost:9160/?worldID=456");
  connection.onclose = function(e) {
    console.log(e.code)
  };
  connection.onmessage = function(message){
    console.log(message.data);
  };
</script>