WJWH · July 16, 2020 20:28 · Jul 16, 2020
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,48 @@
+{-# LANGUAGE OverloadedStrings #-}
+-- Echo server program
+module Main (main) where
+
+import Control.Concurrent
+import Control.Concurrent.MVar
+import qualified Control.Exception as E
+import Control.Monad (unless, forever, void)
+import qualified Data.ByteString as S
+import qualified Data.ByteString.Char8 as S8
+import Network.Socket
+import Network.Socket.ByteString (recv, sendAll)
+
+resp = "HTTP/1.0 200 OK\n\n"
+
+main :: IO ()
+main = do
+  forkIO $ runTCPServer Nothing "3000" (talk)
+  forever $ threadDelay 10000000
+
+
+talk s = do
+    msg <- recv s 1024
+    sendAll s resp
+
+
+-- from the "network-run" package.
+runTCPServer :: Maybe HostName -> ServiceName -> (Socket -> IO a) -> IO a
+runTCPServer mhost port server = withSocketsDo $ do
+    addr <- resolve
+    E.bracket (open addr) close loop
+  where
+    resolve = do
+        let hints = defaultHints {
+                addrFlags = [AI_PASSIVE]
+              , addrSocketType = Stream
+              }
+        head <$> getAddrInfo (Just hints) mhost (Just port)
+    open addr = do
+        sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
+        setSocketOption sock ReuseAddr 1
+        withFdSocket sock setCloseOnExecIfNeeded
+        bind sock $ addrAddress addr
+        listen sock 1024
+        return sock
+    loop sock = forever $ do
+        (conn, _peer) <- accept sock
+        void $ forkFinally (server conn) (const $ gracefulClose conn 5000)