Resurrecting a dead torrent tracker and finding 3M peers

> Is this legal?

Why wouldn't it be? You're not actually hosting a tracker in this case, only looking at incoming connections. And even if you do run a tracker, hard to make the case that the tracker itself is illega. Hosting something like opentrackr is like hosting a search engine, how they respond to legal takedown requests is where the crux is at, and whatever infra sits around the tracker, so police and courts can see/assume the intent. But trackers are pretty stupid coordination server software, would be crazy if they became illegal.

The Anti-Circumvention Clause in the DMCA says "No person shall manufacture, import, offer to the public, provide, or otherwise traffic in any technology [...] is primarily designed or produced for the purpose of circumventing a technological measure that effectively controls access to a work protected under this title [or] has only limited commercially significant purpose or use other than to circumvent a technological measure that effectively controls access to a work protected under this title"

It seems difficult to argue that this would apply, because what would the "technological measure to control access" be that a bittorrent client (or tracker) is circumventing?

I also don't know of any precedent where bittorrent software/client itself was ruled illegal (but am not a lawyer).