The peer_id prefix for uTorrent x.y.z Build m is calculated thus:
- The first eight characters are always -UTxyz0-
- Characters nine and ten are the build number in reverse byte order. These have always been greater than 255 and (so far) lower than 65535, so they equate to two bytes. Convert m to hexadecimal:
2307110 = 5A1F16
- Swap the bytes:
1F 5A
- If they're non-printable characters or any of - . _ ~ then percent-encode them, otherwise convert them to their ASCII representation:
%1fZ
So! The prefixes you requested are:
-UT2200-%1fZ
-UT2210-Bb
-UT3220-To
(Confused? I don't blame you. Just capture these from a tracker announce, it's much easier.)
Note that just changing the prefix isn't going to be enough to get an accurate spoof, as there are other factors involved. With that said, for uTorrent, if you can find a client file for the same version and a build number close to the one you want, you can usually get away with just changing the prefix and User-Agent. Always cross-check it with the real client nonetheless.