与其他模块的套接字通信

Question

我想运行一个websocket服务器并将消息从另一个模块发送到它。

到目前为止，我只设法将一个通道传递给启动服务器的模块。但是我希望拥有全局的writeFile，可以随时从任何模块调用。

我也想有多个客户与sendMessage.一旦连接关闭，我假设线程仍然停留在forever循环中。

服务器.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

主.hs

main :: IO ()
main = do
    client <- createServer
    sendMessage client ("hello" :: ByteString)

Answer 1

我最终使用了带有unsafePerformIO的MVar。虽然不完全推荐，但代码整洁简单。

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

代码仍然缺少异常处理，它仅适用于 1 个连接的客户端。