One of the biggest problems, i think, is that VB is not very godo at binary stuff. Bitmasks, endianness, hashtables, etc. get very tricky. Even simple things like reading nul-terminated strings requires quite a lot of code.

There have been Gnutella projects in VB, but as far as I know none of them have bee nupdated for a long time. The Gnutella protocol has been developed a lot since then.