Do I need a Win32 Hook -- Filesystem stuff

Question

Here is the idea. Essentially I want to know when a VPN client is trying to open certain media types (mp3, wmv, etc) and instead of opening them on the server-side machine, stream them to the VPN client. So how can I know when a file is trying to be opened? This seems like a Win32 Hook to me, but after some reading it seems as though there is no hook into the filesystem. What is the standard way to do this??

Thanks!
Stephen

Stephen · Answer

IP address how? Like from a netstat run or what? I might post in a VPN specific forum or read up on the protocol some more.

Alan · Answer

I don't know much about VPNs but could you distinguish from the IP address?

Stephen · Answer

Yeah that's more of what I was thinking I'll look into that. I have one last question though. Since delving into these filters is a little more than I had originally wanted to do is it possible to edit the context menu in the following way? What I'm envisioning is this: When a user right clicks one of the media types under the file menu would be Stream this file which would stream the file rather than open it in the standard fashion. I know how to edit Explorer's context menus so that isn't a problem. But how can I know whether the right-click request is coming from the VPN or a normal user? Thanks!!!

Alan · Answer

Well it's possible to intercept file system requests by attaching filter device objects as this is the method used by the file monitoring utility FileMon on NT systems: http://technet.microsoft.com/en-us/sysinternals/bb896642.aspx However you'd need to write your own file system filter driver to do this so it's not something that could be done from C#.

Stephen · Answer

Hey thanks for the reply! Unfortunately I already looked into that and it seems as though it only watches for files that are changed. What I need is to be alerted whenever the OS tries to open certain file types stop the normal course of action (say to start Windows Media Player) and instead stream the file to the open VPN client. If someone can think of a different design to do the same thing let me know as I would be very interested in hearing about it!

Alan · Answer

Check out the FileSystemWatcher class: http://msdn.microsoft.com/en-us/library/system.io.filesystemwatcher.aspx