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-- | Simple functions to run UDP clients and servers.
module Network.Run.UDP (
runUDPClient,
runUDPServer,
runUDPServerFork,
) where
import Control.Concurrent (forkFinally, forkIO)
import qualified Control.Exception as E
import Control.Monad (forever, void)
import Data.ByteString (ByteString)
import qualified Data.List.NonEmpty as NE
import Network.Socket
import Network.Socket.ByteString
import Network.Run.Core
-- | Running a UDP client with a socket.
-- The client action takes a socket and
-- server's socket address.
-- They should be used with 'sendTo'.
runUDPClient :: HostName -> ServiceName -> (Socket -> SockAddr -> IO a) -> IO a
runUDPClient host port client = do
addr <- resolve Datagram (Just host) port [AI_ADDRCONFIG] NE.head
let sockAddr = addrAddress addr
E.bracket (openSocket addr) close $ \sock -> client sock sockAddr
-- | Running a UDP server with an open socket in a single Haskell thread.
runUDPServer :: Maybe HostName -> ServiceName -> (Socket -> IO a) -> IO a
runUDPServer mhost port server = do
addr <- resolve Datagram mhost port [AI_PASSIVE] NE.head
E.bracket (openServerSocket addr) close server
-- | Running a UDP server with a connected socket in each Haskell thread.
-- The first request is given to the server.
-- Suppose that the server is serving on __addrS:portS__ and
-- a client connects to the service from __addrC:portC__.
-- A connected socket is created by binding to __*:portS__ and
-- connecting to __addrC:portC__,
-- resulting in __(UDP,addrS:portS,addrC:portC)__ where
-- __addrS__ is given magically.
-- This approach is fragile due to NAT rebidings.
runUDPServerFork
:: [HostName] -> ServiceName -> (Socket -> ByteString -> IO ()) -> IO ()
runUDPServerFork [] _ _ = return ()
runUDPServerFork (h : hs) port server = do
mapM_ (forkIO . run) hs
run h
where
run host = do
labelMe $ "UDP server for " ++ h
runUDPServer (Just host) port $ \lsock -> forever $ do
(bs0, peeraddr) <- recvFrom lsock 2048
let family = case peeraddr of
SockAddrInet{} -> AF_INET
SockAddrInet6{} -> AF_INET6
_ -> error "family"
hints =
defaultHints
{ addrSocketType = Datagram
, addrFamily = family
, addrFlags = [AI_PASSIVE]
}
addr <- NE.head <$> getAddrInfo (Just hints) Nothing (Just port)
s <- openServerSocket addr
connect s peeraddr
void $ forkFinally (labelMe "UDP server" >> server s bs0) (\_ -> close s)
|
