A long time ago I discovered WinPCap which includes packet.dll which contains many low-level packet related functions. It's a 3rd party product of course, so it won't be found by default on people's machines. It also includes 2 other files, the packet driver, and a high level packet related pcap.dll.

On their site they only supported programs written in C/C++ but said that it was probably possible to write VB programs using their dlls.

It's been done. Here's a bonafide packet sniffing program written in VB including source.

http://sourceforge.net/projects/packetvb/

One other note.. as long as you have the driver and dll installed on the system, you may write raw-socket utilities for any windows OS.
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