improving the examples with runners.

Network/Socket.hs

@@ -31,35 +31,35 @@
 -- > import Network.Socket.ByteString (recv, sendAll)
 -- >
 -- > main :: IO ()
--- > main = withSocketsDo $ do
--- >     addr <- resolve "3000"
+-- > main = runTCPServer Nothing "3000" talk
+-- >   where
+-- >     talk s = do
+-- >         msg <- recv s 1024
+-- >         unless (S.null msg) $ do
+-- >           sendAll s msg
+-- >           talk s
+-- >
+-- > 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 port = do
+-- >     resolve = do
 -- >         let hints = defaultHints {
 -- >                 addrFlags = [AI_PASSIVE]
 -- >               , addrSocketType = Stream
 -- >               }
--- >         addr:_ <- getAddrInfo (Just hints) Nothing (Just port)
--- >         return addr
+-- >         head <$> getAddrInfo (Just hints) mhost (Just port)
 -- >     open addr = do
 -- >         sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
 -- >         setSocketOption sock ReuseAddr 1
--- >         -- If the prefork technique is not used,
--- >         -- set CloseOnExec for the security reasons.
 -- >         withFdSocket sock $ setCloseOnExecIfNeeded
--- >         bind sock (addrAddress addr)
--- >         listen sock 10
+-- >         bind sock $ addrAddress addr
+-- >         listen sock 1024
 -- >         return sock
 -- >     loop sock = forever $ do
--- >         (conn, peer) <- accept sock
--- >         putStrLn $ "Connection from " ++ show peer
--- >         void $ forkFinally (talk conn) (\_ -> close conn)
--- >     talk conn = do
--- >         msg <- recv conn 1024
--- >         unless (S.null msg) $ do
--- >           sendAll conn msg
--- >           talk conn
+-- >         (conn, _peer) <- accept sock
+-- >         void $ forkFinally (server conn) (const $ gracefulClose conn 5000)
 --
 -- > {-# LANGUAGE OverloadedStrings #-}
 -- > -- Echo client program
@@ -71,23 +71,24 @@
 -- > import Network.Socket.ByteString (recv, sendAll)
 -- >
 -- > main :: IO ()
--- > main = withSocketsDo $ do
--- >     addr <- resolve "127.0.0.1" "3000"
--- >     E.bracket (open addr) close talk
+-- > main = runTCPClient "127.0.0.1" "3000" $ \s -> do
+-- >     sendAll s "Hello, world!"
+-- >     msg <- recv s 1024
+-- >     putStr "Received: "
+-- >     C.putStrLn msg
+-- >
+-- > runTCPClient :: HostName -> ServiceName -> (Socket -> IO a) -> IO a
+-- > runTCPClient host port client = withSocketsDo $ do
+-- >     addr <- resolve
+-- >     E.bracket (open addr) close client
 -- >   where
--- >     resolve host port = do
+-- >     resolve = do
 -- >         let hints = defaultHints { addrSocketType = Stream }
--- >         addr:_ <- getAddrInfo (Just hints) (Just host) (Just port)
--- >         return addr
+-- >         head <$> getAddrInfo (Just hints) (Just host) (Just port)
 -- >     open addr = do
 -- >         sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
 -- >         connect sock $ addrAddress addr
 -- >         return sock
--- >     talk sock = do
--- >         sendAll sock "Hello, world!"
--- >         msg <- recv sock 1024
--- >         putStr "Received: "
--- >         C.putStrLn msg
 --
 -- The proper programming model is that one 'Socket' is handled by
 -- a single thread. If multiple threads use one 'Socket' concurrently,

examples/EchoClient.hs

@@ -8,20 +8,21 @@ import Network.Socket
 import Network.Socket.ByteString (recv, sendAll)
 
 main :: IO ()
-main = withSocketsDo $ do
-    addr <- resolve "127.0.0.1" "3000"
-    E.bracket (open addr) close talk
+main = runTCPClient "127.0.0.1" "3000" $ \s -> do
+    sendAll s "Hello, world!"
+    msg <- recv s 1024
+    putStr "Received: "
+    C.putStrLn msg
+
+runTCPClient :: HostName -> ServiceName -> (Socket -> IO a) -> IO a
+runTCPClient host port client = withSocketsDo $ do
+    addr <- resolve
+    E.bracket (open addr) close client
   where
-    resolve host port = do
+    resolve = do
         let hints = defaultHints { addrSocketType = Stream }
-        addr:_ <- getAddrInfo (Just hints) (Just host) (Just port)
-        return addr
+        head <$> getAddrInfo (Just hints) (Just host) (Just port)
     open addr = do
         sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
         connect sock $ addrAddress addr
         return sock
-    talk sock = do
-        sendAll sock "Hello, world!"
-        msg <- recv sock 1024
-        putStr "Received: "
-        C.putStrLn msg

examples/EchoServer.hs

@@ -9,32 +9,32 @@ import Network.Socket
 import Network.Socket.ByteString (recv, sendAll)
 
 main :: IO ()
-main = withSocketsDo $ do
-    addr <- resolve "3000"
+main = runTCPServer Nothing "3000" talk
+  where
+    talk s = do
+        msg <- recv s 1024
+        unless (S.null msg) $ do
+          sendAll s msg
+          talk s
+
+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 port = do
+    resolve = do
         let hints = defaultHints {
                 addrFlags = [AI_PASSIVE]
               , addrSocketType = Stream
               }
-        addr:_ <- getAddrInfo (Just hints) Nothing (Just port)
-        return addr
+        head <$> getAddrInfo (Just hints) mhost (Just port)
     open addr = do
         sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
         setSocketOption sock ReuseAddr 1
-        -- If the prefork technique is not used,
-        -- set CloseOnExec for the security reasons.
         withFdSocket sock $ setCloseOnExecIfNeeded
-        bind sock (addrAddress addr)
-        listen sock 10
+        bind sock $ addrAddress addr
+        listen sock 1024
         return sock
     loop sock = forever $ do
-        (conn, peer) <- accept sock
-        putStrLn $ "Connection from " ++ show peer
-        void $ forkFinally (talk conn) (\_ -> close conn)
-    talk conn = do
-        msg <- recv conn 1024
-        unless (S.null msg) $ do
-          sendAll conn msg
-          talk conn
+        (conn, _peer) <- accept sock
+        void $ forkFinally (server conn) (const $ gracefulClose conn 5000)