Hi, The problem is not with the haskell, but with telnet, which uses line buffered output itself. Try the following: module Main(main) where import IO import Network main = do socket <- listenOn (PortNumber 15151) (handle,hostName,_) <- accept socket hSetBuffering handle (BlockBuffering (Just 4096)) putStr ("Accepted: "++hostName++"\n") c <- hGetLine handle putStrLn (show c) telnet to this, type a line and hit return ... should print the line. Regards, Keean Schupke George Russell wrote:
The attached short program (compile with "ghc VServer.hs -o v -package net") is supposed to set up a server on port 15151, wait for a connection, read the first character from the connection, and print it out. Unfortunately if I test it, by running it, and starting up "telnet [machine] 15151" somewhere else, and then type some random text, EG "foo[RETURN]", it does not work. It looks as if the problem is that VServer.hs issues the command hSetBuffering handle (BlockBuffering (Just 4096)) on the connection, because when I change it to hSetBuffering handle NoBuffering the program works.
However this is not what I want to do!! Because setting NoBuffering on the handle is going to mean that when the Server *outputs* something, it will potentially be done very expensively character by character. How do I get block buffering on the Server's output, but not have input to the server held up?
The same thing seems to happen with client Handles by the way.
------------------------------------------------------------------------
-- Test program for server using GHC Socket library. module Main(main) where
import IO import Network
main = do socket <- listenOn (PortNumber 15151) (handle,hostName,_) <- accept socket hSetBuffering handle (BlockBuffering (Just 4096)) putStr ("Accepted: "++hostName++"\n") c <- hGetChar handle putStrLn (show c)