controlling timeout for Network.Socket.connect - how?
Hello, communion people! I have a problem and ask for an advice. I'm dealing with sockets on *Linux* platform (Network.Socket). The problem is that I can't fully control timeout for (connect :: Socket -> SockAddr -> IO ()) operation. On my system the timeout is - 3 seconds - I want to be able to change that in run-time. Well I managed to find out how to make it LESS THAN 3 seconds - using System.Timeout. But how to make timeout bigger (for example 9 seconds) is a mystery. (Notice: in order to achieve 9 seconds timeout - just repeating *connect* 3 times won't be effective for long-slow-way-connections. So it's not a solution.) The source code of Network.Socket.connect, taken from darcs: --------------------------------- -- Connecting a socket -- -- Make a connection to an already opened socket on a given machine -- and port. assumes that we have already called createSocket, -- otherwise it will fail. -- -- This is the dual to $bindSocket$. The {\em server} process will -- usually bind to a port number, the {\em client} will then connect -- to the same port number. Port numbers of user applications are -- normally agreed in advance, otherwise we must rely on some meta -- protocol for telling the other side what port number we have been -- allocated. connect :: Socket -- Unconnected Socket -> SockAddr -- Socket address stuff -> IO () connect sock@(MkSocket s _family _stype _protocol socketStatus) addr = do modifyMVar_ socketStatus $ \currentStatus -> do if currentStatus /= NotConnected then ioError (userError ("connect: can't peform connect on socket in status " ++ show currentStatus)) else do withSockAddr addr $ \p_addr sz -> do let connectLoop = do r <- c_connect s p_addr (fromIntegral sz) if r == -1 then do rc <- c_getLastError case rc of 10093 -> do -- WSANOTINITIALISED withSocketsDo (return ()) r <- c_connect s p_addr (fromIntegral sz) if r == -1 then (c_getLastError >>= throwSocketError "connect") else return r _ -> throwSocketError "connect" rc else return r connectBlocked = do #if !defined(__HUGS__) threadWaitWrite (fromIntegral s) #endif err <- getSocketOption sock SoError if (err == 0) then return 0 else do ioError (errnoToIOError "connect" (Errno (fromIntegral err)) Nothing Nothing) connectLoop return Connected --------------------------------- I know that controlling timeout is somehow connected to select(2) (I'm currently investigating this matter...), but it's not in the Network or Network.Socket libs (but in the libs that they FFI with). Hope I won't have to rewrite these low-level functions.... >__< Could anybody, please share some experience on how to adjust timeout for *connect*? Thanks in advance, Best regards, Belka -- View this message in context: http://www.nabble.com/controlling-timeout-for-Network.Socket.connect---how--... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.
It's hard to belive, that nobody ever tackled/solved the subj. problem. I still can delay a bit solving it, in hope somebody would share experience. Regards, Belka Belka wrote:
Hello, communion people!
I have a problem and ask for an advice. I'm dealing with sockets on *Linux* platform (Network.Socket). The problem is that I can't fully control timeout for (connect :: Socket -> SockAddr -> IO ()) operation. On my system the timeout is - 3 seconds - I want to be able to change that in run-time. Well I managed to find out how to make it LESS THAN 3 seconds - using System.Timeout. But how to make timeout bigger (for example 9 seconds) is a mystery. (Notice: in order to achieve 9 seconds timeout - just repeating *connect* 3 times won't be effective for long-slow-way-connections. So it's not a solution.)
The source code of Network.Socket.connect, taken from darcs: --------------------------------- -- Connecting a socket -- -- Make a connection to an already opened socket on a given machine -- and port. assumes that we have already called createSocket, -- otherwise it will fail. -- -- This is the dual to $bindSocket$. The {\em server} process will -- usually bind to a port number, the {\em client} will then connect -- to the same port number. Port numbers of user applications are -- normally agreed in advance, otherwise we must rely on some meta -- protocol for telling the other side what port number we have been -- allocated.
connect :: Socket -- Unconnected Socket -> SockAddr -- Socket address stuff -> IO ()
connect sock@(MkSocket s _family _stype _protocol socketStatus) addr = do modifyMVar_ socketStatus $ \currentStatus -> do if currentStatus /= NotConnected then ioError (userError ("connect: can't peform connect on socket in status " ++ show currentStatus)) else do withSockAddr addr $ \p_addr sz -> do
let connectLoop = do r <- c_connect s p_addr (fromIntegral sz) if r == -1 then do rc <- c_getLastError case rc of 10093 -> do -- WSANOTINITIALISED withSocketsDo (return ()) r <- c_connect s p_addr (fromIntegral sz) if r == -1 then (c_getLastError >>= throwSocketError "connect") else return r _ -> throwSocketError "connect" rc else return r
connectBlocked = do #if !defined(__HUGS__) threadWaitWrite (fromIntegral s) #endif err <- getSocketOption sock SoError if (err == 0) then return 0 else do ioError (errnoToIOError "connect" (Errno (fromIntegral err)) Nothing Nothing)
connectLoop return Connected
--------------------------------- I know that controlling timeout is somehow connected to select(2) (I'm currently investigating this matter...), but it's not in the Network or Network.Socket libs (but in the libs that they FFI with). Hope I won't have to rewrite these low-level functions.... >__< Could anybody, please share some experience on how to adjust timeout for *connect*?
Thanks in advance, Best regards, Belka
-- View this message in context: http://www.nabble.com/controlling-timeout-for-Network.Socket.connect---how--... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.
Belka ha scritto:
Hello, communion people!
I have a problem and ask for an advice. I'm dealing with sockets on *Linux* platform (Network.Socket). The problem is that I can't fully control timeout for (connect :: Socket -> SockAddr -> IO ()) operation. On my system the timeout is - 3 seconds -
What system? Is the timeout the same with a plain C program? connect timeout is typically 75 seconds. Also note that system timeout is only used when the socket is in blocking mode.
[...] I know that controlling timeout is somehow connected to select(2)
Yes. The only working method is to set the socket to non blocking mode, and use select (or poll/epoll/kqueue).
[...]
Manlio Perillo
Thanks, Manlio!
What system? ArchLinux (2.6.27)
Is the timeout the same with a plain C program? Didn't try yet... ^__^
I know that controlling timeout is somehow connected to select(2) Yes. The only working method is to set the socket to non blocking mode, and use select (or poll/epoll/kqueue).
Thanks, now I'm confident, that am on the right way! ^__^ I wonder, if *select* really blocks the whole process... or blocks just the "green" thread, that called it?.. It doesn't depend from being safe/unsafe FFI-ed, does it? Belka -- View this message in context: http://www.nabble.com/controlling-timeout-for-Network.Socket.connect---how--... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.
Belka ha scritto:
Thanks, Manlio!
What system? ArchLinux (2.6.27)
Is the timeout the same with a plain C program? Didn't try yet... ^__^
I know that controlling timeout is somehow connected to select(2) Yes. The only working method is to set the socket to non blocking mode, and use select (or poll/epoll/kqueue).
Thanks, now I'm confident, that am on the right way! ^__^ I wonder, if *select* really blocks the whole process... or blocks just the "green" thread, that called it?..
select blocks the whole process. But you should really use Control.Concurrent.threadWaitRead. Note that: 1) when connection completes successfully, the socket descriptor becomes writable. 2) in case of errors, the socket descriptor becomes both writable and readable. As pointed in "UNIX Network Programming" (third edition): nonblocking connects are one of the most nonportable areas of network programming. You may check the Twisted framework (if you know Python) to see a sample implementation). Manlio Perillo
It doesn't depend from being safe/unsafe FFI-ed, does it?
Belka
Thanks, Manlio!
What system? A r c h Linux (2.6.27)
Is the timeout the same with a plain C program? Didn't try yet... ^__^
I know that controlling timeout is somehow connected to select(2) Yes. The only working method is to set the socket to non blocking mode, and use select (or poll/epoll/kqueue).
Thanks, now I'm confident, that am on the right way! ^__^ I wonder, if *select* really blocks the whole process... or blocks just the "green" thread, that called it?.. It doesn't depend from being safe/unsafe FFI-ed, does it? Belka -- View this message in context: http://www.nabble.com/controlling-timeout-for-Network.Socket.connect---how--... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.
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Manlio Perillo