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-- | This module implements a bare-bones TCP or Unix socket server.
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RankNTypes #-}
module Network.StreamServer
( streamServer
, ServerHandle
, ServerConfig(..)
, withSession
, quitListening
, dummyServerHandle
) where
import Data.Monoid
import Network.Socket as Socket
import Data.ByteString.Char8
( hGetNonBlocking
)
import qualified Data.ByteString.Char8 as S
( hPutStrLn
)
import System.Directory (removeFile)
import System.IO
( IOMode(..)
, hSetBuffering
, BufferMode(..)
, hWaitForInput
, hClose
, hIsEOF
, hPutStrLn
, stderr
, hFlush
)
import Control.Monad
import Control.Monad.Fix (fix)
import Control.Concurrent (forkIO, threadDelay, ThreadId, mkWeakThreadId)
import Control.Exception (catch,handle,try,finally)
import System.IO.Error (tryIOError)
import System.Mem.Weak
import System.IO.Error
-- import Data.Conduit
import Control.Monad.IO.Class (MonadIO (liftIO))
import qualified Data.ByteString as S (ByteString)
import System.IO (Handle)
import Control.Concurrent.MVar (newMVar)
import Network.SocketLike
data ServerHandle = ServerHandle Socket (Weak ThreadId)
-- | Create a useless do-nothing 'ServerHandle'.
dummyServerHandle :: IO ServerHandle
dummyServerHandle = do
mvar <- newMVar Closed
let sock = MkSocket 0 AF_UNSPEC NoSocketType 0 mvar
thread <- mkWeakThreadId <=< forkIO $ return ()
return (ServerHandle sock thread)
removeSocketFile :: SockAddr -> IO ()
removeSocketFile (SockAddrUnix fname) = removeFile fname
removeSocketFile _ = return ()
-- | Terminate the server accept-loop. Call this to shut down the server.
quitListening :: ServerHandle -> IO ()
quitListening (ServerHandle socket _) =
finally (Socket.getSocketName socket >>= removeSocketFile)
(Socket.close socket)
-- | It's 'bshow' instead of 'show' to enable swapping in a 'ByteString'
-- variation. (This is not exported.)
bshow :: Show a => a -> String
bshow e = show e
-- | Send a string to stderr. Not exported. Default 'serverWarn' when
-- 'withSession' is used to configure the server.
warnStderr :: String -> IO ()
warnStderr str = hPutStrLn stderr str >> hFlush stderr
data ServerConfig = ServerConfig
{ serverWarn :: String -> IO ()
-- ^ Action to report warnings and errors.
, serverSession :: RestrictedSocket -> Int -> Handle -> IO ()
-- ^ Action to handle interaction with a client
}
-- | Initialize a 'ServerConfig' using the provided session handler.
withSession :: (RestrictedSocket -> Int -> Handle -> IO ()) -> ServerConfig
withSession session = ServerConfig warnStderr session
-- | Launch a thread to listen at the given bind address and dispatch
-- to session handler threads on every incomming connection. Supports
-- IPv4 and IPv6, TCP and unix sockets.
--
-- The returned handle can be used with 'quitListening' to terminate the
-- thread and prevent any new sessions from starting. Currently active
-- session threads will not be terminated or signaled in any way.
streamServer :: ServerConfig -> SockAddr -> IO ServerHandle
streamServer cfg addr = do
let warn = serverWarn cfg
family = case addr of
SockAddrInet {} -> AF_INET
SockAddrInet6 {} -> AF_INET6
SockAddrUnix {} -> AF_UNIX
sock <- socket family Stream 0
setSocketOption sock ReuseAddr 1
fix $ \loop ->
tryIOError (removeSocketFile addr) >> bind sock addr
`catchIOError` \e -> do warn $ "bind-error: " <> bshow addr <> " " <> bshow e
threadDelay 5000000
loop
listen sock maxListenQueue
thread <- mkWeakThreadId <=< forkIO $ acceptLoop cfg sock 0
return (ServerHandle sock thread)
-- | Not exported. This, combined with 'acceptException' form a mutually recursive
-- loop that handles incomming connections. To quit the loop, the socket must be
-- closed by 'quitListening'.
acceptLoop :: ServerConfig -> Socket -> Int -> IO ()
acceptLoop cfg sock n = handle (acceptException cfg n sock) $ do
con <- accept sock
let conkey = n + 1
h <- socketToHandle (fst con) ReadWriteMode
forkIO $ serverSession cfg (restrictHandleSocket h (fst con)) conkey h
acceptLoop cfg sock (n + 1)
acceptException :: ServerConfig -> Int -> Socket -> IOError -> IO ()
acceptException cfg n sock ioerror = do
Socket.close sock
case show (ioeGetErrorType ioerror) of
"resource exhausted" -> do -- try again
serverWarn cfg $ ("acceptLoop: resource exhasted")
threadDelay 500000
acceptLoop cfg sock (n + 1)
"invalid argument" -> do -- quit on closed socket
return ()
message -> do -- unexpected exception
serverWarn cfg $ ("acceptLoop: "<>bshow message)
return ()
|
