mrd on 2007-01-19 18:16:31 -0500: > In GHC 6.6 (and HEAD), it seems to block unexpectedly, and this > strange behavior is related to hIsOpen and hIsEOF, somehow. It acts > like hIsOpen or hIsEOF is holding up the loop until input arrives, but > it still blocks at hGetLine. > > The server ends up printing out lines that were typed into the client > a while ago, as if it were stuck on some kind of backlog but could > not catch up.
[...] > > import Control.Concurrent > > import Control.Concurrent.STM > > import System.IO > > import Network > > > main = withSocketsDo $ do > > sock <- listenOn $ PortNumber 9000 > > (h,_,_) <- accept sock From your description it sounds like you have a buffering problem. Have you tried adding 'hSetBuffering h LineBuffering' here? > > ch <- atomically newTChan > > -- thread which pumps lines read > > -- from socket into channel > > forkIO . sequence_ . repeat $ > > hGetLine h >>= atomically . writeTChan ch > > -- main thread just waits for data from channel > > -- and prints it to screen > > sequence_ . repeat $ > > do isOpen <- hIsOpen h > > isEOF <- hIsEOF h > > putStrLn $ "handle isOpen = " ++ show isOpen > > ++ "; isEOF = " ++ show isEOF > > hFlush stdout > > line <- atomically $ readTChan ch > > putStrLn line > > hFlush stdout
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