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