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{-# OPTIONS -cpp #-}
-----------------------------------------------------------------------------
-- |
-- Module : Network
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file libraries/core/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : provisional
-- Portability : portable
--
-- The "Network" interface is a \"higher-level\" interface to
-- networking facilities, and it is recommended unless you need the
-- lower-level interface in "Network.Socket".
--
-----------------------------------------------------------------------------

module Network (

-- * Basic data types
Socket,
        PortID(..),
HostName,
PortNumber, -- instance (Eq, Enum, Num, Real, Integral)

-- * Initialisation
withSocketsDo, -- :: IO a -> IO a

-- * Server-side connections
listenOn, -- :: PortID -> IO Socket
accept, -- :: Socket -> IO (Handle, HostName, PortNumber)

-- * Client-side connections
connectTo, -- :: HostName -> PortID -> IO Handle

-- * Simple sending and receiving
sendTo, -- :: HostName -> PortID -> String -> IO ()
recvFrom, -- :: HostName -> PortID -> IO String

-- * Miscellaneous
socketPort, -- :: Socket -> IO PortID

-- * Networking Issues
-- ** Buffering
{-$buffering-}

-- ** Improving I\/O Performance over sockets
{-$performance-}

-- ** @SIGPIPE@
{-$sigpipe-}

       ) where

#include "config.h"

import Network.BSD
import Network.Socket hiding ( accept, socketPort, recvFrom, sendTo, PortNumber )
import qualified Network.Socket as Socket ( accept )
import System.IO
import Prelude
import Control.Exception as Exception

-- ---------------------------------------------------------------------------
-- High Level ``Setup'' functions

-- If the @PortID@ specifies a unix family socket and the @Hostname@
-- differs from that returned by @getHostname@ then an error is
-- raised. Alternatively an empty string may be given to @connectTo@
-- signalling that the current hostname applies.

data PortID =
Service String -- Service Name eg "ftp"
| PortNumber PortNumber -- User defined Port Number
#if !defined(mingw32_TARGET_OS) && !defined(cygwin32_TARGET_OS) && !defined(_WIN32)
| UnixSocket String -- Unix family socket in file system
#endif

-- | Calling 'connectTo' creates a client side socket which is
-- connected to the given host and port. The Protocol and socket type is
-- derived from the given port identifier. If a port number is given
-- then the result is always an internet family 'Stream' socket.

connectTo :: HostName -- Hostname
-> PortID -- Port Identifier
-> IO Handle -- Connected Socket

connectTo hostname (Service serv) = do
    proto <- getProtocolNumber "tcp"
    bracketOnError
(socket AF_INET Stream proto)
(sClose) -- only done if there's an error
(\sock -> do
          port <- getServicePortNumber serv
          he <- getHostByName hostname
          connect sock (SockAddrInet port (hostAddress he))
          socketToHandle sock ReadWriteMode
  )

connectTo hostname (PortNumber port) = do
    proto <- getProtocolNumber "tcp"
    bracketOnError
(socket AF_INET Stream proto)
(sClose) -- only done if there's an error
        (\sock -> do
       he <- getHostByName hostname
       connect sock (SockAddrInet port (hostAddress he))
       socketToHandle sock ReadWriteMode
)

#if !defined(mingw32_TARGET_OS) && !defined(cygwin32_TARGET_OS) && !defined(_WIN32)
connectTo _ (UnixSocket path) = do
    bracketOnError
(socket AF_UNIX Stream 0)
(sClose)
(\sock -> do
          connect sock (SockAddrUnix path)
          socketToHandle sock ReadWriteMode
)
#endif

-- | Creates the server side socket which has been bound to the
-- specified port.
--
-- NOTE: To avoid the \"Address already in use\"
-- problems popped up several times on the GHC-Users mailing list we
-- set the 'ReuseAddr' socket option on the listening socket. If you
-- don't want this behaviour, please use the lower level
-- 'Network.Socket.listen' instead.

listenOn :: PortID -- ^ Port Identifier
-> IO Socket -- ^ Connected Socket

listenOn (Service serv) = do
    proto <- getProtocolNumber "tcp"
    bracketOnError
        (socket AF_INET Stream proto)
(sClose)
(\sock -> do
port <- getServicePortNumber serv
setSocketOption sock ReuseAddr 1
bindSocket sock (SockAddrInet port iNADDR_ANY)
listen sock maxListenQueue
return sock
)

listenOn (PortNumber port) = do
    proto <- getProtocolNumber "tcp"
    bracketOnError
     (socket AF_INET Stream proto)
(sClose)
(\sock -> do
setSocketOption sock ReuseAddr 1
bindSocket sock (SockAddrInet port iNADDR_ANY)
listen sock maxListenQueue
return sock
)

#if !defined(mingw32_TARGET_OS) && !defined(cygwin32_TARGET_OS) && !defined(_WIN32)
listenOn (UnixSocket path) =
    bracketOnError
     (socket AF_UNIX Stream 0)
(sClose)
(\sock -> do
setSocketOption sock ReuseAddr 1
bindSocket sock (SockAddrUnix path)
listen sock maxListenQueue
return sock
)
#endif

-- -----------------------------------------------------------------------------
-- accept

-- | Accept a connection on a socket created by 'listenOn'. Normal
-- I\/O opertaions (see "System.IO") can be used on the 'Handle'
-- returned to communicate with the client.
-- Notice that although you can pass any Socket to Network.accept, only
-- sockets of either AF_UNIX or AF_INET will work (this shouldn't be a problem,
-- though). When using AF_UNIX, HostName will be set to the path of the socket
-- and PortNumber to -1.
--
accept :: Socket -- ^ Listening Socket
       -> IO (Handle,
HostName,
PortNumber) -- ^ Triple of: read\/write 'Handle' for
-- communicating with the client,
-- the 'HostName' of the peer socket, and
-- the 'PortNumber' of the remote connection.
accept sock@(MkSocket _ AF_INET _ _ _) = do
 ~(sock', (SockAddrInet port haddr)) <- Socket.accept sock
 peer <- Exception.catchJust ioErrors
(do
(HostEntry peer _ _ _) <- getHostByAddr AF_INET haddr
return peer
)
(\e -> inet_ntoa haddr)
-- if getHostByName fails, we fall back to the IP address
 handle <- socketToHandle sock' ReadWriteMode
 return (handle, peer, port)
#if !defined(mingw32_TARGET_OS) && !defined(cygwin32_TARGET_OS) && !defined(_WIN32)
accept sock@(MkSocket _ AF_UNIX _ _ _) = do
 ~(sock', (SockAddrUnix path)) <- Socket.accept sock
 handle <- socketToHandle sock' ReadWriteMode
 return (handle, path, -1)
#endif
accept sock@(MkSocket _ family _ _ _) =
  error $ "Sorry, address family " ++ (show family) ++ " is not supported!"

-- -----------------------------------------------------------------------------
-- sendTo/recvFrom

-- Send and recived data from/to the given host and port number. These
-- should normally only be used where the socket will not be required for
-- further calls.

sendTo :: HostName -- Hostname
       -> PortID -- Port Number
       -> String -- Message to send
       -> IO ()
sendTo h p msg = do
  s <- connectTo h p
  hPutStr s msg
  hClose s

recvFrom :: HostName -- Hostname
-> PortID -- Port Number
-> IO String -- Received Data
recvFrom host port = do
 ip <- getHostByName host
 let ipHs = hostAddresses ip
 s <- listenOn port
 let
  waiting = do
     ~(s', SockAddrInet _ haddr) <- Socket.accept s
     he <- getHostByAddr AF_INET haddr
     if not (any (`elem` ipHs) (hostAddresses he))
      then do
         sClose s'
         waiting
      else do
h <- socketToHandle s' ReadMode
        msg <- hGetContents h
        return msg

 message <- waiting
 return message

-- ---------------------------------------------------------------------------
-- Access function returning the port type/id of socket.

-- | Returns the 'PortID' associated with a given socket.
socketPort :: Socket -> IO PortID
socketPort s = do
    sockaddr <- getSocketName s
    return (portID sockaddr)
  where
   portID sa =
    case sa of
     SockAddrInet port _ -> PortNumber port
#if !defined(mingw32_TARGET_OS) && !defined(cygwin32_TARGET_OS) && !defined(_WIN32)
     SockAddrUnix path -> UnixSocket path
#endif

-- ---------------------------------------------------------------------------
-- Utils

-- Like bracket, but only performs the final action if there was an
-- exception raised by the middle bit.
bracketOnError
:: IO a -- ^ computation to run first (\"acquire resource\")
-> (a -> IO b) -- ^ computation to run last (\"release resource\")
-> (a -> IO c) -- ^ computation to run in-between
-> IO c -- returns the value from the in-between computation
bracketOnError before after thing =
  block (do
    a <- before
    r <- Exception.catch
(unblock (thing a))
(\e -> do { after a; throw e })
    return r
 )

-----------------------------------------------------------------------------
-- Extra documentation

{-$buffering

The 'Handle' returned by 'connectTo' and 'accept' is block-buffered by
default. For an interactive application you may want to set the
buffering mode on the 'Handle' to
'LineBuffering' or 'NoBuffering', like so:

> h <- connectTo host port
> hSetBuffering h LineBuffering
-}

{-$performance

For really fast I\/O, it might be worth looking at the 'hGetBuf' and
'hPutBuf' family of functions in "System.IO".
-}

{-$sigpipe

On Unix, when reading from a socket and the writing end is
closed by the remote client, the program is normally sent a
@SIGPIPE@ signal by the operating system. The
default behaviour when a @SIGPIPE@ is received is
to terminate the program silently, which can be somewhat confusing
if you haven't encountered this before. The solution is to
specify that @SIGPIPE@ is to be ignored, using
the POSIX library:

> import Posix
> main = do installHandler sigPIPE Ignore Nothing; ...
-}
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