Communicate with socket from other module - sockets

Question

I'd like to run a websocket server and send messages from another module to it.
So far I have only managed to pass a channel to the module which starts the server. But I'd like to have as globally as writeFile which can be called from any module at any time.
Also I'd like to have multiple clients with sendMessage. Once a connection closes I assume the thread still stays in the forever loop.
Server.hs
import Network.WebSockets
import Control.Concurrent
import Control.Monad
import Data.ByteString
createServer :: IO (Chan ByteString)
createServer = do
chan <- newChan
forkIO $ runServer "127.0.0.1" 8080 (serverApp chan)
ready <- readChan chan -- wait for client
return chan
serverApp :: Chan ByteString -> PendingConnection -> IO ()
serverApp chan pending =
do
print "Client connected"
connection <- acceptRequest pending
writeChan chan "ready"
forever $ do
msg <- readChan chan
sendTextData connection msg
sendMessage :: Chan ByteString -> ByteString -> IO ()
sendMessage = writeChan
Main.hs
main :: IO ()
main = do
client <- createServer
sendMessage client ("hello" :: ByteString)

Answer 1

I ended up using an MVar with unsafePerformIO. While not exactly recommended the the code is neat and simple.
createServer :: IO ()
createServer = do
_ <- forkIO $ runServer "127.0.0.1" 8080 serverApp
return ()
serverApp :: PendingConnection -> IO ()
serverApp pending =
do
connection <- acceptRequest pending
forever $ do
msg <- takeMVar channel
sendTextData connection msg
channel :: MVar ByteString
{-# NOINLINE channel #-}
channel = unsafePerformIO newEmptyMVar
sendMessage :: ByteString -> IO ()
sendMessage = putMVar channel
The code is still missing exception handling and it only works for 1 connected client.