Question

I asked a question about signal on windows with the same code,here is another question

import IO
import Control.Exception hiding (catch)
import Control.Concurrent
import Network

main = withSocketsDo $ do {main'}
main' = listenOn (PortNumber 9900) >>= acceptConnections

acceptConnections sock = do
        putStrLn $ "trying to accept" ++ (show sock)-- debug msg
        conn@(h,host,port) <- accept sock
        print conn -- debug msg
        forkIO $ catch (talk conn `finally` hClose h) (\e -> print e)
        acceptConnections sock

talk conn@(h,_,_) = hGetLine h >>= hPutStrLn h >> hFlush h >> talk conn

I run the program on win7,and it looks like the socket created succeed,but I can’t telnet on,and netstat doesn’t show any listening socket with the process,is there anything wrong?Or,haskell has bug on windows?(By the way,on debian with this code works perfect)

Answer 1

when I use netstat -a on win7,I found the listening ip with port 9900 is [::],neither is 127.0.0.1 nor 0.0.0.0,so I guess the problem is during create socket in function “listenOn”,then I wrote “listenOn2” replaced.And the problem is solved.
Here is the full code:(the only difference is change the proto from [[getProtocolNumber “tcp”]] to [[defaultProtocol]]),maybe this is a bug.

import IO
import Control.Exception hiding (catch)
import Control.Concurrent
import Network
import Network.Socket
listenOn2 (PortNumber port) = do
        --proto <- getProtocolNumber "tcp"  ,here is the difference!!!!
        let proto = defaultProtocol
        bracketOnError
            (socket AF_INET Stream proto)
            (sClose)
            (\sock -> do
                setSocketOption sock ReuseAddr 1
                --addr <- inet_addr "127.0.0.1"
                bindSocket sock (SockAddrInet port iNADDR_ANY)
                listen sock maxListenQueue
                return sock
            )
main = withSocketsDo $ do {main'}
main' = listenOn2 (PortNumber 9900) >>= acceptConnections

acceptConnections sock = do
        putStrLn $ "trying to accept" ++ (show sock)-- debug msg
        conn@(h,host,port) <- Network.accept sock
        print conn -- debug msg
        forkIO $ catch (talk conn `finally` hClose h) (\e -> print e)
        acceptConnections sock

talk conn@(h,_,_) = hGetLine h >>= hPutStrLn h >> hFlush h >> talk conn