Socket6-0.19 (from cpan) builds fine for me on ActiveState's 64-bit version of build 822 (perl 5.8.8), and passes the test suite.
I used the previously-mentioned SDK (which comes with its own nmake). I don't have Visual Studio at all.
If you want the build, /msg me your email address and I'll send it over. Or do you need a version suitable for use with 5.10 ?