I received an explanation of the level 8 vulnerability via private chat, after hanging around in IRC for ~10 hours. By that point, I knew about (and easily implemented) SSH, and had inferred several other useful tidbits, but didn't quite understand the port-counting vulnerability. Partly, as I had a mental block against "timing attacks" based on the instructions ... this was not technically a timing attack, but was certainly very timing dependent.

I still wrote the code myself.