If I understand you correctly you need a StablePtr to your Connection value. Please see: http://www.haskell.org/ghc/docs/latest/html/libraries/base-4.6.0.1/Foreign-S... Best regards, Krzysztof Skrzętnicki On Thu, Feb 28, 2013 at 6:31 PM, C K Kashyap wrote:

I am using http://hackage.haskell.org/package/connection. So I create network connection in Haskell

getConnection :: IO Connection

I'd like this connection to be returned to C so that subsequent calls from C can send in the connection handle.

Regards, Kashyap

On Thu, Feb 28, 2013 at 9:04 PM, Niklas Hambüchen wrote:

...

What data type are you dealing with exactly?

If you have a socket, I guess you can just use it from C (via FFI).

PS: By "Network.Connection", do you mean http://hackage.haskell.org/package/network-connection-0.1.1 ? Seems deprecated.

On 28/02/13 06:14, C K Kashyap wrote:

...

Hi, I am using Network.Connection to connect to gmail in my Haskell module - that's compiled to DLL and invoked from C.

I need a mechanism to return the connection handle to C so that it can pass it in the subsequent calls. How can I achieve this?

Regards, Kashyap

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Okay, for now I have figured out a working solution to the original problem I was facing ..... I just forkIO another IO action that does the actual network work and in addition, it opens a server socket and waits for commands. The calls from C reach Haskell, from where a connection is made to the server and command is sent. A little convoluted but works. I have the whole implementation here - https://github.com/ckkashyap/gmail So now I am able to create a standalone, self sufficient DLL that I can just hand off to the folks in my org and they can write a C program and connect to gmail!!!! Hey Donn ... when you say, implement the IO in C, you also imply implementing the SSL stuff too right? ... that's one thing I wanted to avoid - and I was also reluctant to use something like openSSL because that would come in the way of making standalone, self - sufficient DLL. I really have to see what kind of performance hit my DLL has ... Regards, Kashyap On Fri, Mar 1, 2013 at 12:07 AM, Donn Cave wrote:

Quoth C K Kashyap ,

...

I am using http://hackage.haskell.org/package/connection. So I create network connection in Haskell

getConnection :: IO Connection

I'd like this connection to be returned to C so that subsequent calls from C can send in the connection handle.

According to the documentation, he doesn't export enough of the Connection type to access the handle inside, and there appears to be no function provided to do that either. So it looks to me like you'd have to 1) make the connection "by hand" with Network.Socket.connect etc., 2) get the Socket fd, 3) make a Handle from the Socket, 4) pass that to connectFromHandle, and 5) use the fd with your C function.

Note that the socket connection itself, represented by the fd that you return to C, will simply transmit data back and forth without modification. Specifically without SSL encryption. If you need SSL encryption in both Haskell and C, it would probably be simpler to implement the I/O in C and call it from Haskell.

Donn

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