Not sure why you're having issues, I just tried it on GHC 7.6.3 on Fedora 20 and it worked fine there as well (both with runhaskell or compiled with -O). I might start adding putStrLn statements to the code to see where it's unexpectedly blocking, or perhaps use 127.0.0.1 instead of "localhost" in case the issue is a DNS misconfiguration. On Tue, May 20, 2014 at 10:51 PM, yang.zhao wrote:

thanks for your replay. i run the two program in two different teriminal for sure.

it works for you? but why can't run well on my computer.

make me creazy....

2014-05-21 13:47 GMT+08:00 Bob Ippolito :

How precisely are you trying to run the client? Are you typing it in to

...

the same terminal? If so, then the client is never actually started, because when you type ./cli the input is going to ./serv and not the shell. Try running the client in a separate terminal.

It works for me here on Mac OS X 10.9.2 with GHC 7.8.2.

On Tue, May 20, 2014 at 10:42 PM, yang.zhao wrote:

...

hi guys, I'm newbie, just begin to learn Haskell. now i write a very simple server and client .

Server: import Control.Concurrent import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do s <- listenOn $ PortNumber $ fromIntegral port (h, _, _) <- accept s

sline <- hGetLine h hPutStrLn h sline putStrLn $ "send "++sline threadDelay 1000000

hClose h sClose s

Client : import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do h <- connectTo "localhost" $ PortNumber $ fromIntegral port hPutStrLn h "hello" bs <- hGetContents h putStrLn bs hClose h

And, it doesn't work now . I run ./serv , then run ./cli , they will block all the time. but, when i run ./serv, and telnet localhost 1234 in another terminal, it works fine. so i don't know what's the wrong with my code. anybody can tell me about my problem?

os is Debian 7, haskell-platform 2012.2.0.0

thanks a lot!!! -- K.I.S.S.

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

-- K.I.S.S.

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I don't have a GHC installation that old, but I think that a bug in that version of GHC is the only reasonable explanation for this. I highly recommend that you upgrade to GHC 7.8.x or at least 7.6.x. Lazy IO is a bit unsafe and error-prone in some scenarios. hGetContents doesn't really do any reading from the handle until the input is demanded, which is why you can print "read from handle done" but not the contents of bs. On Tue, May 20, 2014 at 11:10 PM, yang.zhao wrote:

Here's my new code:

$ cat serv.hs

import Control.Concurrent import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do s <- listenOn $ PortNumber $ fromIntegral port putStrLn "Listening..."

(h, _, _) <- accept s putStrLn "After accept" sline <- hGetLine h putStrLn "get line from handle"

hPutStrLn h sline putStrLn $ "send "++sline threadDelay 1000000

hClose h sClose s

-------- $ cat clie.hs

import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do h <- connectTo "127.0.0.1" $ PortNumber $ fromIntegral port putStrLn "After connect" hPutStrLn h "hello" putStrLn "put hello to handle done" bs <- hGetContents h putStrLn "read from handle done" putStrLn bs hClose h

=== one terminal, run ./serv, then run ./clie in another terminal. Output is :

$ ./serv Listening... After accept

$ ./clie After connect put hello to handle done read from handle done

it seems that client has read from then handle, but donesn't read anything, then block. and server donesn't receive anything, still wait for something...

ghc version is 7.4.1, because of this?..

2014-05-21 13:57 GMT+08:00 Bob Ippolito :

Not sure why you're having issues, I just tried it on GHC 7.6.3 on Fedora

...

20 and it worked fine there as well (both with runhaskell or compiled with -O).

I might start adding putStrLn statements to the code to see where it's unexpectedly blocking, or perhaps use 127.0.0.1 instead of "localhost" in case the issue is a DNS misconfiguration.

On Tue, May 20, 2014 at 10:51 PM, yang.zhao wrote:

...

thanks for your replay. i run the two program in two different teriminal for sure.

it works for you? but why can't run well on my computer.

make me creazy....

2014-05-21 13:47 GMT+08:00 Bob Ippolito :

How precisely are you trying to run the client? Are you typing it in to

...

the same terminal? If so, then the client is never actually started, because when you type ./cli the input is going to ./serv and not the shell. Try running the client in a separate terminal.

It works for me here on Mac OS X 10.9.2 with GHC 7.8.2.

On Tue, May 20, 2014 at 10:42 PM, yang.zhao wrote:

...

hi guys, I'm newbie, just begin to learn Haskell. now i write a very simple server and client .

Server: import Control.Concurrent import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do s <- listenOn $ PortNumber $ fromIntegral port (h, _, _) <- accept s

sline <- hGetLine h hPutStrLn h sline putStrLn $ "send "++sline threadDelay 1000000

hClose h sClose s

Client : import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do h <- connectTo "localhost" $ PortNumber $ fromIntegral port hPutStrLn h "hello" bs <- hGetContents h putStrLn bs hClose h

And, it doesn't work now . I run ./serv , then run ./cli , they will block all the time. but, when i run ./serv, and telnet localhost 1234 in another terminal, it works fine. so i don't know what's the wrong with my code. anybody can tell me about my problem?

os is Debian 7, haskell-platform 2012.2.0.0

thanks a lot!!! -- K.I.S.S.

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

-- K.I.S.S.

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

-- K.I.S.S.

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

hGetContents reads a handle until EOF, so you've implement a deadlock. The server is waiting to read a second line, but the client is waiting for the server to close the socket in order to do the first print. Perhaps you meant to use hGetLine instead? On Wed, May 21, 2014 at 12:15 AM, yang.zhao wrote:

omg, i test it on Windows, it's ok now. GHC is 7.6.3. i really don't konw why this happen..

but there is another question on Windows

main = withSocketsDo $ do s <- listenOn $ PortNumber $ fromIntegral port putStrLn "Listening..." (h, _, _) <- accept s putStrLn "After accept" sline <- hGetLine h putStrLn $ "get line from handle"++sline hPutStrLn h "xxxx...." putStrLn "send first done"

--second recv slinea <- hGetLine h putStrLn $ "get line from handle"++slinea

hPutStrLn h "yyyy....." putStrLn "send second done"

threadDelay 1000000 -- cli:

main = withSocketsDo $ do h <- connectTo "127.0.0.1" $ PortNumber $ fromIntegral port putStrLn "After connect" hPutStrLn h "xxx" putStrLn "put first to handle done"

bs <- hGetContents h putStrLn "read from handle done " putStrLn bs

--second send hPutStrLn h "yyy" putStrLn "put second to handle done" bfs <- hGetContents h

putStrLn "read from handle done " putStrLn bs

the second send and recv is blocking... server's output: Listening... After accept get line from handlexxx send first done

client's output: After connect put first to handle done read from handle done xxx....

..... T_T

2014-05-21 14:10 GMT+08:00 yang.zhao :

Here's my new code:

...

$ cat serv.hs

import Control.Concurrent import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do s <- listenOn $ PortNumber $ fromIntegral port putStrLn "Listening..."

(h, _, _) <- accept s putStrLn "After accept" sline <- hGetLine h putStrLn "get line from handle"

hPutStrLn h sline putStrLn $ "send "++sline threadDelay 1000000

hClose h sClose s

-------- $ cat clie.hs

import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do h <- connectTo "127.0.0.1" $ PortNumber $ fromIntegral port putStrLn "After connect" hPutStrLn h "hello" putStrLn "put hello to handle done" bs <- hGetContents h putStrLn "read from handle done" putStrLn bs hClose h

=== one terminal, run ./serv, then run ./clie in another terminal. Output is :

$ ./serv Listening... After accept

$ ./clie After connect put hello to handle done read from handle done

it seems that client has read from then handle, but donesn't read anything, then block. and server donesn't receive anything, still wait for something...

ghc version is 7.4.1, because of this?..

2014-05-21 13:57 GMT+08:00 Bob Ippolito :

Not sure why you're having issues, I just tried it on GHC 7.6.3 on Fedora

...

20 and it worked fine there as well (both with runhaskell or compiled with -O).

I might start adding putStrLn statements to the code to see where it's unexpectedly blocking, or perhaps use 127.0.0.1 instead of "localhost" in case the issue is a DNS misconfiguration.

On Tue, May 20, 2014 at 10:51 PM, yang.zhao wrote:

...

thanks for your replay. i run the two program in two different teriminal for sure.

it works for you? but why can't run well on my computer.

make me creazy....

2014-05-21 13:47 GMT+08:00 Bob Ippolito :

How precisely are you trying to run the client? Are you typing it in to

...

the same terminal? If so, then the client is never actually started, because when you type ./cli the input is going to ./serv and not the shell. Try running the client in a separate terminal.

It works for me here on Mac OS X 10.9.2 with GHC 7.8.2.

On Tue, May 20, 2014 at 10:42 PM, yang.zhao wrote:

...

hi guys, I'm newbie, just begin to learn Haskell. now i write a very simple server and client .

Server: import Control.Concurrent import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do s <- listenOn $ PortNumber $ fromIntegral port (h, _, _) <- accept s

sline <- hGetLine h hPutStrLn h sline putStrLn $ "send "++sline threadDelay 1000000

hClose h sClose s

Client : import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do h <- connectTo "localhost" $ PortNumber $ fromIntegral port hPutStrLn h "hello" bs <- hGetContents h putStrLn bs hClose h

And, it doesn't work now . I run ./serv , then run ./cli , they will block all the time. but, when i run ./serv, and telnet localhost 1234 in another terminal, it works fine. so i don't know what's the wrong with my code. anybody can tell me about my problem?

os is Debian 7, haskell-platform 2012.2.0.0

thanks a lot!!! -- K.I.S.S.

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

-- K.I.S.S.

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

-- K.I.S.S.

-- K.I.S.S.

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

Thank you very much, Bob and Sylvain. i test hGetLine instead of hGetContents. 2014-05-21 16:07 GMT+08:00 Sylvain Henry :

hGetContents puts the handle in semi-closed state and reads until there is nothing left to read. Hence you have a deadlock. Use hGetLine in "cli".

Sylvain

2014-05-21 9:15 GMT+02:00 yang.zhao :

omg, i test it on Windows, it's ok now. GHC is 7.6.3.

...

i really don't konw why this happen..

but there is another question on Windows

main = withSocketsDo $ do s <- listenOn $ PortNumber $ fromIntegral port putStrLn "Listening..." (h, _, _) <- accept s putStrLn "After accept" sline <- hGetLine h putStrLn $ "get line from handle"++sline hPutStrLn h "xxxx...." putStrLn "send first done"

--second recv slinea <- hGetLine h putStrLn $ "get line from handle"++slinea

hPutStrLn h "yyyy....." putStrLn "send second done"

threadDelay 1000000 -- cli:

main = withSocketsDo $ do h <- connectTo "127.0.0.1" $ PortNumber $ fromIntegral port putStrLn "After connect" hPutStrLn h "xxx" putStrLn "put first to handle done"

bs <- hGetContents h putStrLn "read from handle done " putStrLn bs

--second send hPutStrLn h "yyy" putStrLn "put second to handle done" bfs <- hGetContents h

putStrLn "read from handle done " putStrLn bs

the second send and recv is blocking... server's output: Listening... After accept get line from handlexxx send first done

client's output: After connect put first to handle done read from handle done xxx....

..... T_T

2014-05-21 14:10 GMT+08:00 yang.zhao :

Here's my new code:

...

$ cat serv.hs

import Control.Concurrent import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do s <- listenOn $ PortNumber $ fromIntegral port putStrLn "Listening..."

(h, _, _) <- accept s putStrLn "After accept" sline <- hGetLine h putStrLn "get line from handle"

hPutStrLn h sline putStrLn $ "send "++sline threadDelay 1000000

hClose h sClose s

-------- $ cat clie.hs

import System.IO import Network

port :: Int port = 1234

main :: IO () main = withSocketsDo $ do h <- connectTo "127.0.0.1" $ PortNumber $ fromIntegral port putStrLn "After connect" hPutStrLn h "hello" putStrLn "put hello to handle done" bs <- hGetContents h putStrLn "read from handle done" putStrLn bs hClose h

=== one terminal, run ./serv, then run ./clie in another terminal. Output is :

$ ./serv Listening... After accept

$ ./clie After connect put hello to handle done read from handle done

it seems that client has read from then handle, but donesn't read anything, then block. and server donesn't receive anything, still wait for something...

ghc version is 7.4.1, because of this?..

2014-05-21 13:57 GMT+08:00 Bob Ippolito :

Not sure why you're having issues, I just tried it on GHC 7.6.3 on

...

Fedora 20 and it worked fine there as well (both with runhaskell or compiled with -O).

I might start adding putStrLn statements to the code to see where it's unexpectedly blocking, or perhaps use 127.0.0.1 instead of "localhost" in case the issue is a DNS misconfiguration.

On Tue, May 20, 2014 at 10:51 PM, yang.zhao wrote:

...

thanks for your replay. i run the two program in two different teriminal for sure.

it works for you? but why can't run well on my computer.

make me creazy....

2014-05-21 13:47 GMT+08:00 Bob Ippolito :

How precisely are you trying to run the client? Are you typing it in

...

to the same terminal? If so, then the client is never actually started, because when you type ./cli the input is going to ./serv and not the shell. Try running the client in a separate terminal.

It works for me here on Mac OS X 10.9.2 with GHC 7.8.2.

On Tue, May 20, 2014 at 10:42 PM, yang.zhao wrote:

> hi guys, > I'm newbie, just begin to learn Haskell. > now i write a very simple server and client . > > Server: > import Control.Concurrent > import System.IO > import Network > > port :: Int > port = 1234 > > main :: IO () > main = withSocketsDo $ do > s <- listenOn $ PortNumber $ fromIntegral port > (h, _, _) <- accept s > > sline <- hGetLine h > hPutStrLn h sline > putStrLn $ "send "++sline > threadDelay 1000000 > > hClose h > sClose s > > Client : > import System.IO > import Network > > port :: Int > port = 1234 > > main :: IO () > main = withSocketsDo $ do > h <- connectTo "localhost" $ PortNumber $ fromIntegral port > hPutStrLn h "hello" > bs <- hGetContents h > putStrLn bs > hClose h > > > And, it doesn't work now . I run ./serv , then run ./cli , they will > block all the time. > but, when i run ./serv, and telnet localhost 1234 in another > terminal, it works fine. > so i don't know what's the wrong with my code. > anybody can tell me about my problem? > > os is Debian 7, haskell-platform 2012.2.0.0 > > thanks a lot!!! > -- > K.I.S.S. > > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners > >

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

-- K.I.S.S.

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

-- K.I.S.S.

-- K.I.S.S.

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

-- K.I.S.S.