WinpkFilter is the development framework for designing low-level network applications. With WinpkFilter you can implement custom firewall, internet connection sharing(NAT), IP shaper, VPN and many other low-level network solutions completely in user-mode using your favorite development environment: Visual C++, Delphi, C++ Builder and etc. It consists of an NT kernel driver (ndisrd.sys), virtual device driver (ndisrd.vxd), IOCTL interface wrapper DLL (ndisapi.dll) and several samples (ListAdapters, PacketSniffer, PassThru). WinpkFilter does not require you to be experienced in kernel mode programming; it provides you with user level API instead. However, if you need to implement your solution (because of performance issues) in kernel then to your satisfaction raw IOCTL interface is also available.

WinpkFilter Developer Edition is the Shareware version. The full version can be purchased by clicking on the "CLICK HERE TO ORDER" button below for around  1,495.00USD.