Merge PR #448.

Author: kazu-yamamoto

Network/Socket.hs

@@ -52,16 +52,19 @@
 -- >               , addrSocketType = Stream
 -- >               }
 -- >         head <$> getAddrInfo (Just hints) mhost (Just port)
--- >     open addr = do
--- >         sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
+-- >     open addr = E.bracketOnError (openSocket addr) close $ \sock -> do
 -- >         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)
+-- >     loop sock = forever $ E.bracketOnError (accept sock) (close . fst)
+-- >         $ \(conn, _peer) -> void $
+-- >             -- 'forkFinally' alone is unlikely to fail thus leaking @conn@,
+-- >             -- but 'E.bracketOnError' above will be necessary if some
+-- >             -- non-atomic setups (e.g. spawning a subprocess to handle
+-- >             -- @conn@) before proper cleanup of @conn@ is your case
+-- >             forkFinally (server conn) (const $ gracefulClose conn 5000)
 --
 -- > {-# LANGUAGE OverloadedStrings #-}
 -- > -- Echo client program
@@ -88,8 +91,7 @@
 -- >     resolve = do
 -- >         let hints = defaultHints { addrSocketType = Stream }
 -- >         head <$> getAddrInfo (Just hints) (Just host) (Just port)
--- >     open addr = do
--- >         sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
+-- >     open addr = E.bracketOnError (openSocket addr) close $ \sock -> do
 -- >         connect sock $ addrAddress addr
 -- >         return sock
 --

examples/EchoClient.hs

@@ -23,7 +23,6 @@ runTCPClient host port client = withSocketsDo $ do
     resolve = do
         let hints = defaultHints { addrSocketType = Stream }
         head <$> getAddrInfo (Just hints) (Just host) (Just port)
-    open addr = do
-        sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
+    open addr = E.bracketOnError (openSocket addr) close $ \sock -> do
         connect sock $ addrAddress addr
         return sock

examples/EchoServer.hs

@@ -29,13 +29,16 @@ runTCPServer mhost port server = withSocketsDo $ do
               , addrSocketType = Stream
               }
         head <$> getAddrInfo (Just hints) mhost (Just port)
-    open addr = do
-        sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
+    open addr = E.bracketOnError (openSocket addr) close $ \sock -> do
         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)
+    loop sock = forever $ E.bracketOnError (accept sock) (close . fst)
+        $ \(conn, _peer) -> void $
+            -- 'forkFinally' alone is unlikely to fail thus leaking @conn@,
+            -- but 'E.bracketOnError' above will be necessary if some
+            -- non-atomic setups (e.g. spawning a subprocess to handle
+            -- @conn@) before proper cleanup of @conn@ is your case
+            forkFinally (server conn) (const $ gracefulClose conn 5000)