Works like a charm now :) Thank you for the insight. Robin.

Hi there,

looks like a network byte-order vs host byte-order gotcha. Never use the PortNum constructor, but declare 'portnum' to have type PortNumber and simply drop the use of PortNum in your code alltogether. Alternatively, use intToPortNumber to translate between Int and PortNumber.

hth --sigbjorn

----- Original Message ----- From: "robin abraham" To: Sent: Wednesday, January 28, 2004 21:57 Subject: Network problem with ghc on WinXP

...

Hi,

I have ghc-6.0.1 on WinXP and Solaris. I have a simple echo server (server.hs given below) and client (client.hs given below) and I encounter the following: 1) server.hs compiled and running on Solaris: a) client.hs (Solaris) can connect. b) client.hs (WinXP) cannot connect. c) telnet (WinXP) can connect. d) telnet (Solaris) can connect. e) Scan of port 3000 shows server is listening.

2) server.hs compiled and running on WinXP: a) client.hs (Solaris) cannot connect. b) client.hs (WinXP) can connect. c) telnet (WinXP) cannot connect. d) telnet (Solaris) cannot connect. e) Scan of ports does not show server.

Basically, when the server is running on WinXP, only the Haskell program client.hs (also running on the same WinXP machine) can "converse" with it through the socket connection. To verify this, I wrote a client in C# - from the WinXP machine, it can connect to server running on my Solaris machine but not to server on the same WinXP machine.

Why isn't the server program on WinXP not behaving itself? Any help/guidance would be highly appreciated.

Thank you. Robin.

-- server.hs module Main where

import SocketPrim import Concurrent import System (getArgs,exitFailure) import Exception(finally) import MVar import IO

server_sock :: IO (Socket) server_sock = do s <- socket AF_INET Stream 6 setSocketOption s ReuseAddr 1 bindSocket s (SockAddrInet (PortNum portnum) iNADDR_ANY) listen s 2 return s

echo_server :: Socket -> IO () echo_server s = do (s', clientAddr) <- accept s h <- socketToHandle s' ReadWriteMode proc <- read_data s' 0 putStrLn ("server processed "++(show proc)++" bytes") sClose s' where read_data sock totalbytes = do str <- recv sock 18 putStrLn ("Server recv: " ++ str) if ((length str) >= 18) then do putStrLn ("Server read: " ++ str) writ <- send sock str putStrLn ("Server wrote: " ++ str) read_data sock $! (totalbytes+(length $! str)) else do putStrLn ("server read: " ++ str) return totalbytes

message = "Hello there sailor" portnum = 3000

main = withSocketsDo $ do { ~[n] <- getArgs; ssock <- server_sock; s <- myForkIO (echo_server ssock); join s; putStrLn "join s"; }

myForkIO :: IO () -> IO (MVar ()) myForkIO io = do mvar <- newEmptyMVar forkIO (io `finally` putMVar mvar ()) return mvar

join :: MVar () -> IO () join mvar = readMVar mvar

-- end of server.hs

-- ***********************************************

-- client.hs

module Main where

import SocketPrim import Concurrent import System (getArgs,exitFailure) import Exception(finally) import MVar import IO

local = "128.193.39.108" message = "Hello there sailor" portnum = 3000

client_sock = do s <- socket AF_INET Stream 6 ia <- inet_addr local connect s (SockAddrInet (PortNum portnum) ia) return s

echo_client n = do s <- client_sock drop <- server_echo s n sClose s where server_echo sock n = if n > 0 then do send sock message putStrLn ("Client wrote: " ++ message) str <- recv sock 19 if (str /= message) then do putStrLn ("Client read error: " ++ str) exitFailure else do putStrLn ("Client read success") server_echo sock (n-1) else do putStrLn "Client read nil" return []

main = withSocketsDo $ do ~[n] <- getArgs c <- myForkIO (echo_client (read n::Int)) join c putStrLn "join c"

myForkIO :: IO () -> IO (MVar ()) myForkIO io = do mvar <- newEmptyMVar forkIO (io `finally` putMVar mvar ()) return mvar

join :: MVar () -> IO () join mvar = readMVar mvar

-- end of client.hs