{-# LANGUAGE CPP #-} -- | This module exports functions that abstract simple TCP 'NS.Socket' -- usage patterns. -- -- This module uses 'MonadIO' and 'C.MonadMask' extensively so that you can -- reuse these functions in monads other than 'IO'. However, if you don't care -- about any of that, just pretend you are using the 'IO' monad all the time -- and everything will work as expected. -- Some code in this file was adapted from the @pipes-network@ library by -- Renzo Carbonara. Copyright (c) 2012-2013. See its licensing terms (BSD3) at: -- https://github.com/k0001/pipes-network/blob/master/LICENSE -- -- Some code in this file was adapted from the @network-conduit@ library by -- Michael Snoyman. Copyright (c) 2011. See its licensing terms (BSD3) at: -- https://github.com/snoyberg/conduit/blob/master/network-conduit/LICENSE module Network.Simple.TCP ( -- * Introduction to TCP networking -- $tcp-101 -- * Client side -- $client-side connect -- * Server side -- $server-side , serve -- ** Listening , listen -- ** Accepting , accept , acceptFork -- * Utils , recv , send -- * Low level support , bindSock , connectSock , closeSock -- * Note to Windows users , NS.withSocketsDo -- * Types , HostPreference(..) -- ** Re-exported from @Network.Socket@ , NS.HostName , NS.ServiceName , NS.Socket , NS.SockAddr ) where import Control.Concurrent (ThreadId, forkIO) import qualified Control.Exception as E import qualified Control.Monad.Catch as C import Control.Monad import Control.Monad.IO.Class (MonadIO(liftIO)) import qualified Data.ByteString as BS import Data.List (partition) import qualified Network.Socket as NS import Network.Simple.Internal import qualified Network.Socket.ByteString as NSB -------------------------------------------------------------------------------- -- $tcp-101 -- -- This introduction aims to give you a overly simplified overview of some -- concepts you need to know about TCP sockets in order to make effective use of -- this module. -- -- There are two ends in a single TCP connection: one is the TCP «server» and -- the other is the TCP «client». Each end is uniquely identified by an IP -- address and a TCP port pair, and each end knows the IP address and TCP port -- of the other end. Each end can send and receive data to and from the other -- end. -- -- A TCP server, once «bound» to a well-known IP address and TCP port, starts -- «listening» for incoming connections from TCP clients to such bound IP -- address and TCP port. When a TCP client attempts to connect to the TCP -- server, the TCP server must «accept» the incoming connection in order to -- start exchanging data with the remote end. A single TCP server can -- sequentially accept many incoming connections, possibly handling each one -- concurrently. -- -- A TCP client can «connect» to a well-known IP address and TCP port previously -- bound by a listening TCP server willing to accept new incoming connections. -- Once the connection is established, the TCP client can immediately start -- exchanging data with the TCP server. The TCP client is randomly assigned a -- TCP port when connecting, and its IP address is selected by the operating -- system so that it is reachable from the remote end. -- -- The TCP client a and the TCP server can be running in the same host or in -- different hosts. -------------------------------------------------------------------------------- -- $client-side -- -- Here's how you could run a TCP client: -- -- @ -- 'connect' \"www.example.org\" \"80\" $ \\(connectionSocket, remoteAddr) -> do -- putStrLn $ \"Connection established to \" ++ show remoteAddr -- -- Now you may use connectionSocket as you please within this scope, -- -- possibly using 'recv' and 'send' to interact with the remote end. -- @ -- | Connect to a TCP server and use the connection. -- -- The connection socket is closed when done or in case of exceptions. -- -- If you prefer to acquire and close the socket yourself, then use -- 'connectSock' and 'closeSock'. connect :: (MonadIO m, C.MonadMask m) => NS.HostName -- ^Server hostname. -> NS.ServiceName -- ^Server service port. -> ((NS.Socket, NS.SockAddr) -> m r) -- ^Computation taking the communication socket -- and the server address. -> m r connect host port = C.bracket (connectSock host port) (silentCloseSock . fst) -------------------------------------------------------------------------------- -- $server-side -- -- Here's how you can run a TCP server that handles in different threads each -- incoming connection to port @8000@ at IPv4 address @127.0.0.1@: -- -- @ -- 'serve' ('Host' \"127.0.0.1\") \"8000\" $ \\(connectionSocket, remoteAddr) -> do -- putStrLn $ \"TCP connection established from \" ++ show remoteAddr -- -- Now you may use connectionSocket as you please within this scope, -- -- possibly using 'recv' and 'send' to interact with the remote end. -- @ -- -- If you need more control on the way your server runs, then you can use more -- advanced functions such as 'listen', 'accept' and 'acceptFork'. -------------------------------------------------------------------------------- -- | Start a TCP server that accepts incoming connections and handles them -- concurrently in different threads. -- -- Any acquired network resources are properly closed and discarded when done or -- in case of exceptions. -- -- Note: This function performs 'listen' and 'acceptFork', so you don't need to -- perform those manually. serve :: MonadIO m => HostPreference -- ^Preferred host to bind. -> NS.ServiceName -- ^Service port to bind. -> ((NS.Socket, NS.SockAddr) -> IO ()) -- ^Computation to run in a different thread -- once an incoming connection is accepted. Takes the -- connection socket and remote end address. -> m () serve hp port k = liftIO $ do listen hp port $ \(lsock,_) -> do forever $ acceptFork lsock k -------------------------------------------------------------------------------- -- | Bind a TCP listening socket and use it. -- -- The listening socket is closed when done or in case of exceptions. -- -- If you prefer to acquire and close the socket yourself, then use 'bindSock', -- 'closeSock' and the 'NS.listen' function from "Network.Socket" instead. -- -- Note: 'N.maxListenQueue' is tipically 128, which is too small for high -- performance servers. So, we use the maximum between 'N.maxListenQueue' and -- 2048 as the default size of the listening queue. The 'NS.NoDelay' and -- 'NS.ReuseAddr' options are set on the socket. listen :: (MonadIO m, C.MonadMask m) => HostPreference -- ^Preferred host to bind. -> NS.ServiceName -- ^Service port to bind. -> ((NS.Socket, NS.SockAddr) -> m r) -- ^Computation taking the listening socket and -- the address it's bound to. -> m r listen hp port = C.bracket listen' (silentCloseSock . fst) where listen' = do x@(bsock,_) <- bindSock hp port liftIO . NS.listen bsock $ max 2048 NS.maxListenQueue return x -------------------------------------------------------------------------------- -- | Accept a single incoming connection and use it. -- -- The connection socket is closed when done or in case of exceptions. accept :: (MonadIO m, C.MonadMask m) => NS.Socket -- ^Listening and bound socket. -> ((NS.Socket, NS.SockAddr) -> m r) -- ^Computation to run once an incoming -- connection is accepted. Takes the connection socket -- and remote end address. -> m r accept lsock k = do conn@(csock,_) <- liftIO (NS.accept lsock) C.finally (k conn) (silentCloseSock csock) {-# INLINABLE accept #-} -- | Accept a single incoming connection and use it in a different thread. -- -- The connection socket is closed when done or in case of exceptions. acceptFork :: MonadIO m => NS.Socket -- ^Listening and bound socket. -> ((NS.Socket, NS.SockAddr) -> IO ()) -- ^Computation to run in a different thread -- once an incoming connection is accepted. Takes the -- connection socket and remote end address. -> m ThreadId acceptFork lsock k = liftIO $ do conn@(csock,_) <- NS.accept lsock forkFinally (k conn) (\ea -> do silentCloseSock csock either E.throwIO return ea) {-# INLINABLE acceptFork #-} -------------------------------------------------------------------------------- -- | Obtain a 'NS.Socket' connected to the given host and TCP service port. -- -- The obtained 'NS.Socket' should be closed manually using 'closeSock' when -- it's not needed anymore, otherwise you risk having the socket open for much -- longer than needed. -- -- Prefer to use 'connect' if you will be using the socket within a limited -- scope and would like it to be closed immediately after its usage or in case -- of exceptions. connectSock :: MonadIO m => NS.HostName -> NS.ServiceName -> m (NS.Socket, NS.SockAddr) connectSock host port = liftIO $ do (addr:_) <- NS.getAddrInfo (Just hints) (Just host) (Just port) E.bracketOnError (newSocket addr) closeSock $ \sock -> do let sockAddr = NS.addrAddress addr NS.connect sock sockAddr return (sock, sockAddr) where hints = NS.defaultHints { NS.addrFlags = [NS.AI_ADDRCONFIG] , NS.addrSocketType = NS.Stream } -- | Obtain a 'NS.Socket' bound to the given host name and TCP service port. -- -- The obtained 'NS.Socket' should be closed manually using 'closeSock' when -- it's not needed anymore. -- -- Prefer to use 'listen' if you will be listening on this socket and using it -- within a limited scope, and would like it to be closed immediately after its -- usage or in case of exceptions. bindSock :: MonadIO m => HostPreference -> NS.ServiceName -> m (NS.Socket, NS.SockAddr) bindSock hp port = liftIO $ do addrs <- NS.getAddrInfo (Just hints) (hpHostName hp) (Just port) let addrs' = case hp of HostIPv4 -> prioritize isIPv4addr addrs HostIPv6 -> prioritize isIPv6addr addrs _ -> addrs tryAddrs addrs' where hints = NS.defaultHints { NS.addrFlags = [NS.AI_PASSIVE] , NS.addrSocketType = NS.Stream } tryAddrs [] = error "bindSock: no addresses available" tryAddrs [x] = useAddr x tryAddrs (x:xs) = E.catch (useAddr x) (\e -> let _ = e :: IOError in tryAddrs xs) useAddr addr = E.bracketOnError (newSocket addr) closeSock $ \sock -> do let sockAddr = NS.addrAddress addr NS.setSocketOption sock NS.NoDelay 1 NS.setSocketOption sock NS.ReuseAddr 1 NS.bindSocket sock sockAddr return (sock, sockAddr) -- | Close the 'NS.Socket'. closeSock :: MonadIO m => NS.Socket -> m () closeSock = liftIO . #if MIN_VERSION_network(2,4,0) NS.close #else NS.sClose #endif {-# INLINE closeSock #-} -------------------------------------------------------------------------------- -- Utils -- | Read up to a limited number of bytes from a socket. -- -- Returns `Nothing` if the remote end closed the connection or end-of-input was -- reached. The number of returned bytes might be less than the specified limit. recv :: MonadIO m => NS.Socket -> Int -> m (Maybe BS.ByteString) recv sock nbytes = do bs <- liftIO (NSB.recv sock nbytes) if BS.null bs then return Nothing else return (Just bs) {-# INLINABLE recv #-} -- | Writes the given bytes to the socket. send :: MonadIO m => NS.Socket -> BS.ByteString -> m () send sock = \bs -> liftIO (NSB.sendAll sock bs) {-# INLINABLE send #-} -------------------------------------------------------------------------------- -- Misc newSocket :: NS.AddrInfo -> IO NS.Socket newSocket addr = NS.socket (NS.addrFamily addr) (NS.addrSocketType addr) (NS.addrProtocol addr) isIPv4addr, isIPv6addr :: NS.AddrInfo -> Bool isIPv4addr x = NS.addrFamily x == NS.AF_INET isIPv6addr x = NS.addrFamily x == NS.AF_INET6 -- | Move the elements that match the predicate closer to the head of the list. -- Sorting is stable. prioritize :: (a -> Bool) -> [a] -> [a] prioritize p = uncurry (++) . partition p -------------------------------------------------------------------------------- -- | 'Control.Concurrent.forkFinally' was introduced in base==4.6.0.0. We'll use -- our own version here for a while, until base==4.6.0.0 is widely establised. forkFinally :: IO a -> (Either E.SomeException a -> IO ()) -> IO ThreadId forkFinally action and_then = E.mask $ \restore -> forkIO $ E.try (restore action) >>= and_then -- | Like 'closeSock', except it swallows all 'IOError' exceptions. silentCloseSock :: MonadIO m => NS.Socket -> m () silentCloseSock sock = liftIO $ do E.catch (closeSock sock) (\e -> let _ = e :: IOError in return ())