Re: [Haskell-cafe] UDP

[Manlio Perillo]

Andrew Coppin ha scritto:

[...]

Yeah, I just assumed that the bind step was only necessary for 
connection-oriented protocols. (Interestingly enough, the matching 
"send" program doesn't bind at all, yet seems to work fine...)




For a client (that is, when you call connect), the kernel chooses the 
source IP address once the socket is connected.


Of course, for a server this is not feasible, since the address *must* 
be know to external programs, if they want to connect to the server.



For more details, I really suggest to read a good book like
"UNIX Network Programming", by W. Richard Stevens.



Regards  Manlio Perillo
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Re: [Haskell-cafe] UDP

[Vimal]

2009/2/1 Andrew Coppin :

>
> Yeah, I just assumed that the bind step was only necessary for
> connection-oriented protocols. (Interestingly enough, the matching "send"
> program doesn't bind at all, yet seems to work fine...)
>

socket() system call creates a socket (a descriptor) that you can
identify. bind() creates an identity for the socket so that
applications outside can refer to it (using ip:port); it also enables
the kernel to pass the received data to your application. sendto()
doesn't require that identity.

-- 
Vimal
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Re: [Haskell-cafe] UDP

[Andrew Coppin]

John Van Enk wrote:

Try something like this:

module Main where

import Network.Socket

main = withSocketsDo $ do
-- Make a UDP socket
s <- socket AF_INET Datagram defaultProtocol

-- We want to listen on all interfaces (0.0.0.0)
bindAddr <- inet_addr "0.0.0.0"

-- Bind to 0.0.0.0:3 
bindSocket s (SockAddrInet 3 bindAddr)

-- Read a message of max length 1000 from some one
(msg,len,from) <- recvFrom s 1000

putStrLn $ "Got the following message from " ++ (show from)
putStrLn msg

Does this help? As Stephan said, you missed the bind step.


That works great, thanks.

Yeah, I just assumed that the bind step was only necessary for 
connection-oriented protocols. (Interestingly enough, the matching 
"send" program doesn't bind at all, yet seems to work fine...)


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Re: [Haskell-cafe] UDP

[Thomas DuBuisson]

On Sat, Jan 31, 2009 at 9:36 PM, Andrew Coppin
 wrote:
> Thomas DuBuisson wrote:
>>
>> The network library is no more than an FFI library to a Berkeley
>> socket interface and as such it implicitly expects you to know sockets
>> already (eg. from programming in C).  One advantage here is reading
>> man pages actually helps (unlike with most Haskell coding) and you can
>> also make equivalent C programs to test things out.
>>
>
> Yes, that's kind of the problem; I don't know how to do this at the C level,
> and I can't seem to Google it. :-}
>
> Ah well, I'll ask around. Somebody must know. ;-)

Ahh, then see Beej's guide [1] if you wish to learn at the C level.

On another note: when making your Haskell app if you are at all
performance concerned then you should use network-bytestring [2].

[1] http://beej.us/guide/bgnet/
[2] 
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/network-bytestring
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Re: [Haskell-cafe] UDP

[Andrew Coppin]

Thomas DuBuisson wrote:

The network library is no more than an FFI library to a Berkeley
socket interface and as such it implicitly expects you to know sockets
already (eg. from programming in C).  One advantage here is reading
man pages actually helps (unlike with most Haskell coding) and you can
also make equivalent C programs to test things out.
  


Yes, that's kind of the problem; I don't know how to do this at the C 
level, and I can't seem to Google it. :-}


Ah well, I'll ask around. Somebody must know. ;-)


In the long term we should design and build a more functional network library.
  


Well, I guess having a library that gives you low-level access means 
that anybody who wants to have a go can easily build something nicer on 
top of that. (As opposed to, say, file I/O where there is only the 
high-level interface, so if you want to do something that isn't 
implemented... you can't.)


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Re: [Haskell-cafe] UDP

[John Van Enk]

Try something like this:
module Main where

import Network.Socket

main = withSocketsDo $ do
-- Make a UDP socket
s <- socket AF_INET Datagram defaultProtocol

-- We want to listen on all interfaces (0.0.0.0)
bindAddr <- inet_addr "0.0.0.0"

-- Bind to 0.0.0.0:3
bindSocket s (SockAddrInet 3 bindAddr)

-- Read a message of max length 1000 from some one
(msg,len,from) <- recvFrom s 1000

putStrLn $ "Got the following message from " ++ (show from)
putStrLn msg

Does this help? As Stephan said, you missed the bind step.

/jve


On Sun, Jan 25, 2009 at 11:22 AM, Andrew Coppin  wrote:

> I'm trying to write a simple program that involves UDP. I was hoping
> something like this would work:
>
> module Main where
>
> import Network.Socket
>
> main = withSocketsDo main2
>
> main2 = do
>  s <- socket AF_INET Datagram defaultProtocol
>  putStrLn "Waiting..."
>  x <- recv s 100
>  putStrLn x
>
> Unfortunately, that doesn't work at all. It immediately throws an exception
> ("unknown error"). But then, the whole module seems to be completely
> undocumented. I managed to find a tiny amount of info online about the
> underlying C API, but I still don't get how the Haskell interface is
> supposed to be used. Any hints?
>
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Re: [Haskell-cafe] UDP

[Thomas DuBuisson]

The network library is no more than an FFI library to a Berkeley
socket interface and as such it implicitly expects you to know sockets
already (eg. from programming in C).  One advantage here is reading
man pages actually helps (unlike with most Haskell coding) and you can
also make equivalent C programs to test things out.

In the long term we should design and build a more functional network library.

Thomas

On Sat, Jan 31, 2009 at 9:19 PM, Stephan Friedrichs
 wrote:
> Andrew Coppin wrote:
>> I'm trying to write a simple program that involves UDP. I was hoping
>> something like this would work:
>>
>> [...]
>
> How about using bindSocket? At least that's the main difference between
> your code snippet and our (UDP-using) barracuda project :)
>
>>
>> main2 = do
>>  s <- socket AF_INET Datagram defaultProtocol
>  bindSocket s ...
>>  putStrLn "Waiting..."
>>  x <- recv s 100
>>  putStrLn x
>>
>> [...]
>>
>
> //Stephan
>
> --
>
> Früher hieß es ja: Ich denke, also bin ich.
> Heute weiß man: Es geht auch so.
>
>  - Dieter Nuhr
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Re: [Haskell-cafe] UDP

[Stephan Friedrichs]

Andrew Coppin wrote:
> I'm trying to write a simple program that involves UDP. I was hoping
> something like this would work:
> 
> [...]

How about using bindSocket? At least that's the main difference between
your code snippet and our (UDP-using) barracuda project :)

> 
> main2 = do
>  s <- socket AF_INET Datagram defaultProtocol
  bindSocket s ...
>  putStrLn "Waiting..."
>  x <- recv s 100
>  putStrLn x
> 
> [...]
> 

//Stephan

-- 

Früher hieß es ja: Ich denke, also bin ich.
Heute weiß man: Es geht auch so.

 - Dieter Nuhr
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Re: [Haskell-cafe] UDP client/server

[John Ky]

Nevermind,

I just got the client to work:

echoClient :: IO ()
echoClient = withSocketsDo $ do
   sock <- socket AF_INET Datagram 0
   n <- sendTo sock "hi" (SockAddrInet echoPort 0x0107f)
   return ()

Thanks everyone for your help.

-John

On 1/12/07, John Ky <[EMAIL PROTECTED] > wrote:Hi,

What's wrong with my UDP client?

echoClient :: IO ()
echoClient = withSocketsDo $ do
   putStrLn "[a]"
   sock <- socket AF_INET Datagram 0
   putStrLn "[b]"
   connect sock (SockAddrInet 9900 iNADDR_ANY)
   putStrLn "[c]"
   n <- send sock "hi"
   putStrLn "[d]"
   return ()

I get:

*Main> echoClient
[a]
[b]
*** Exception: connect: failed (Cannot assign requested address
(WSAEADDRNOTAVAI
L))

Thanks

-John
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Re: [Haskell-cafe] UDP client/server

[John Ky]

Hi,

What's wrong with my UDP client?

echoClient :: IO ()
echoClient = withSocketsDo $ do
   putStrLn "[a]"
   sock <- socket AF_INET Datagram 0
   putStrLn "[b]"
   connect sock (SockAddrInet 9900 iNADDR_ANY)
   putStrLn "[c]"
   n <- send sock "hi"
   putStrLn "[d]"
   return ()

I get:

*Main> echoClient
[a]
[b]
*** Exception: connect: failed (Cannot assign requested address
(WSAEADDRNOTAVAI
L))

Thanks

-John


On 1/12/07, Gregory Wright <[EMAIL PROTECTED]> wrote:



Hi John,

On Jan 11, 2007, at 10:35 AM, Gregory Wright wrote:

>
> Hi John,
>
> On Jan 11, 2007, at 1:58 AM, John Ky wrote:
>
>> Hello,
>>
>> Does anyone know where I can find a simple UDP client/server
>> written in Haskell?
>>
>> Something along the lines of an echo server would do.
>>
>> Thanks
>>
>> -John
>>
>
> Try:
>
>



For testing, you need only use

gregory-wrights-powerbook-g4-17> nc -ul -p 9900 127.0.0.1

and whatever you type should be echoed.  My original description
of how to test:
>
> On my OS X/ppc 10.4.8 system, the above builds with ghc 6.6 and if
> I open one
> terminal with
>
> gregory-wrights-powerbook-g4-17> nc -u 127.0.0.1 9900
>
> and another with
>
> gregory-wrights-powerbook-g4-17> nc -ul -p 9900 127.0.0.1
>
> whatever I type into the first terminal appears on the second.  You
> may have to
> consult your documentation for the options to your version of nc
> (or netcat,
> if you use that instead).

is wrong.  (It will copy from one terminal to the other when the
daemon is not present.)

Best,
Greg


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Re: [Haskell-cafe] UDP client/server

[Gregory Wright]

Hi John,

On Jan 11, 2007, at 10:35 AM, Gregory Wright wrote:



Hi John,

On Jan 11, 2007, at 1:58 AM, John Ky wrote:


Hello,

Does anyone know where I can find a simple UDP client/server  
written in Haskell?


Something along the lines of an echo server would do.

Thanks

-John



Try:






For testing, you need only use

gregory-wrights-powerbook-g4-17> nc -ul -p 9900 127.0.0.1

and whatever you type should be echoed.  My original description
of how to test:


On my OS X/ppc 10.4.8 system, the above builds with ghc 6.6 and if  
I open one

terminal with

gregory-wrights-powerbook-g4-17> nc -u 127.0.0.1 9900

and another with

gregory-wrights-powerbook-g4-17> nc -ul -p 9900 127.0.0.1

whatever I type into the first terminal appears on the second.  You  
may have to
consult your documentation for the options to your version of nc  
(or netcat,

if you use that instead).


is wrong.  (It will copy from one terminal to the other when the  
daemon is not present.)


Best,
Greg

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Re: [Haskell-cafe] UDP client/server

[Gregory Wright]

Hi John,

On Jan 11, 2007, at 1:58 AM, John Ky wrote:


Hello,

Does anyone know where I can find a simple UDP client/server  
written in Haskell?


Something along the lines of an echo server would do.

Thanks

-John



Try:

--
-- UDPEchoServer.hs: Exactly what the name says, a datagram echo server.
--


module Main (main) where

import Network.Socket
import System.Posix.Directory
import System.Posix.Files
import System.Posix.IO
import System.Posix.Process
import System.Exit


echoPort = 9900
maxline = 1500

--
-- The daemon infrastructure
--

main :: IO ()
main = do
  pid <- forkProcess child
  exitImmediately ExitSuccess


child :: IO ()
child = do
  -- Set up the working directory, mask and standard i/o
  -- for a daemon process (these will be inherited by
  -- the forked process):

  changeWorkingDirectory "/"
  setFileCreationMask 0

  mapM_ closeFd [stdInput, stdOutput, stdError]
  nullFd <- openFd "/dev/null" ReadWrite Nothing  
defaultFileFlags

  mapM_ (dupTo nullFd) [stdInput, stdOutput, stdError]

  closeFd nullFd

  createSession -- This child becomes a process and session
-- group leader. This prevents the child of
-- this process (the daemon) from
-- ever getting a controlling terminal.
  pid' <- forkProcess echoserver

  exitImmediately ExitSuccess

--
-- The echo server daemon
--

echoserver :: IO ()
echoserver = do
  withSocketsDo $ do
  sock <- socket AF_INET Datagram 0
  bindSocket sock (SockAddrInet echoPort iNADDR_ANY)
  socketEcho sock


socketEcho :: Socket -> IO ()
socketEcho sock = do
  (mesg, recv_count, client) <- recvFrom sock maxline
  send_count <- sendTo sock mesg client
  socketEcho sock



 
---



On my OS X/ppc 10.4.8 system, the above builds with ghc 6.6 and if I  
open one

terminal with

gregory-wrights-powerbook-g4-17> nc -u 127.0.0.1 9900

and another with

gregory-wrights-powerbook-g4-17> nc -ul -p 9900 127.0.0.1

whatever I type into the first terminal appears on the second.  You  
may have to
consult your documentation for the options to your version of nc (or  
netcat,

if you use that instead).

I was also able to see that the server returned packets using hping3.

Needless to say, the above is just an example, and is by no means  
bulletproof.
I think I adapted it from something I found on the old wiki and  
updated it

to work with the current libraries.

Best Wishes,
Greg




 
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Re: [Haskell-cafe] UDP client/server

[Dan Mead]

I think he meant something more along the lines of (or exactly) this, but in
Haskell

http://java.sun.com/docs/books/tutorial/networking/sockets/clientServer.html

I for one would also be interested in reading a tutorial like this using the
ghc libs

-Dan

On 1/11/07, Henning Thielemann <[EMAIL PROTECTED]> wrote:



On Thu, 11 Jan 2007, John Ky wrote:

> Does anyone know where I can find a simple UDP client/server written in
> Haskell?

There is some support as part of a SuperCollider wrapper:
http://www.slavepianos.org/rd/sw/sw-69/Sound/OpenSoundControl/UDP.hs
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Re: [Haskell-cafe] UDP client/server

[Henning Thielemann]

On Thu, 11 Jan 2007, John Ky wrote:

> Does anyone know where I can find a simple UDP client/server written in
> Haskell?

There is some support as part of a SuperCollider wrapper:
 http://www.slavepianos.org/rd/sw/sw-69/Sound/OpenSoundControl/UDP.hs
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