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------------------------------------------------------------------------------ --- Library to support network programming with sockets that are addressed --- by symbolic names. In contrast to raw sockets (see library --- <code>Socket</code>), this library uses the Curry Port Name Server --- to provide sockets that are addressed by symbolic names --- rather than numbers. --- --- In standard applications, the server side uses the operations --- <code>listenOn</code> and <code>socketAccept</code> to provide some service --- on a named socket, and the client side uses the operation --- <code>connectToSocket</code> to request a service. --- --- @author Michael Hanus --- @version February 2008 --- @category general ------------------------------------------------------------------------------ module NamedSocket(Socket, listenOn, socketAccept, waitForSocketAccept, connectToSocketRepeat, connectToSocketWait, sClose, socketName, connectToSocket) where import System import IO(Handle) import qualified Socket import CPNS --------------------------------------------------------------------- -- Server side operations: --- Abstract type for named sockets. data Socket = NamedSocket String Socket.Socket --- Creates a server side socket with a symbolic name. listenOn :: String -> IO Socket listenOn socketname = do (port,socket) <- Socket.listenOnFresh registerPort socketname port 0 return (NamedSocket socketname socket) --- Returns a connection of a client to a socket. --- The connection is returned as a pair consisting of a string identifying --- the client (the format of this string is implementation-dependent) --- and a handle to a stream communication with the client. --- The handle is both readable and writable. socketAccept :: Socket -> IO (String,Handle) socketAccept (NamedSocket _ socket) = Socket.socketAccept socket --- Waits until a connection of a client to a socket is available. --- If no connection is available within the time limit, it returns Nothing, --- otherwise the connection is returned as a pair consisting --- of a string identifying the client --- (the format of this string is implementation-dependent) --- and a handle to a stream communication with the client. --- @param socket - a socket --- @param timeout - milliseconds to wait for input (< 0 : no time out) waitForSocketAccept :: Socket -> Int -> IO (Maybe (String,Handle)) waitForSocketAccept (NamedSocket _ socket) = Socket.waitForSocketAccept socket --- Closes a server socket. sClose :: Socket -> IO () sClose (NamedSocket socketname socket) = do Socket.sClose socket unregisterPort socketname --- Returns a the symbolic name of a named socket. socketName :: Socket -> String socketName (NamedSocket socketname _) = socketname --------------------------------------------------------------------- -- Client side operations: --- Waits for connection to a Unix socket with a symbolic name. --- In contrast to <code>connectToSocket</code>, this action waits until --- the socket has been registered with its symbolic name. --- @param waittime - the time to wait before retrying (in milliseconds) --- @param action - I/O action to be executed before each wait cycle --- @param retries - number of retries before giving up (-1 = retry forever) --- @param nameAtHost - the symbolic name of the socket --- (must be either of the form "name@host" or "name" --- where the latter is a shorthand for "name@localhost") --- @return Nothing (if connection is not possible within the given limits) --- or (Just h) where h is the handle of the connection connectToSocketRepeat :: Int -> IO _ -> Int -> String -> IO (Maybe Handle) connectToSocketRepeat waittime action retries nameAtHost = do let (name,atHost) = break (=='@') nameAtHost host = if atHost=="" then "localhost" else tail atHost -- check whether remote CPNS demon is alive: alive <- cpnsAlive waittime host if not alive then tryAgain else do -- get remote socket/port numbers: (snr,_) <- getPortInfo name host if snr==0 then tryAgain else Socket.connectToSocket host snr >>= return . Just where tryAgain = if retries==0 then return Nothing else do action sleep (ms2s waittime) connectToSocketRepeat waittime action (decr retries) nameAtHost ms2s n = let mn = n `div` 1000 in if mn==0 then 1 else mn decr n = if n<0 then n else n-1 --- Waits for connection to a Unix socket with a symbolic name and --- return the handle of the connection. --- This action waits (possibly forever) until the socket with the symbolic --- name is registered. --- @param nameAtHost - the symbolic name of the socket --- (must be either of the form "name@host" or "name" --- where the latter is a shorthand for "name@localhost") --- @return the handle of the connection (connected to the socket nameAtHost) --- which is both readable and writable connectToSocketWait :: String -> IO Handle connectToSocketWait nameAtHost = do Just hdl <- connectToSocketRepeat 1000 done (-1) nameAtHost return hdl --- Creates a new connection to an existing(!) Unix socket with a symbolic --- name. If the symbolic name is not registered, an error is reported. --- @param nameAtHost - the symbolic name of the socket --- (must be either of the form "name@host" or "name" --- where the latter is a shorthand for "name@localhost") --- @return the handle of the stream (connected to the socket nameAtHost) --- which is both readable and writable connectToSocket :: String -> IO Handle connectToSocket nameAtHost = do let (name,atHost) = break (=='@') nameAtHost host = if atHost=="" then "localhost" else tail atHost -- get remote port number: (snr,_) <- getPortInfo name host if snr==0 then error ("connectToSocket: Socket \""++name++"@"++host++ "\" is not registered!") else done Socket.connectToSocket host snr --------------------------------------------------------------------- |