Awesome stuff, thanks for posting this. How can one check to see if it works? Are there any stats that can be read either from the directory or by sending commands to the process?
When the seeder is initialy run, it displays a real-time update of the stats of connected peers although the info it provides isn't always 100% reliable (at least not in my experience).
I find the best way is to check if it's working is by running your wallet, making sure that no nodes are available in yourcoin.config file. If the wallet doesn't pick up any new connections after a few seconds (but give it a minute or two to test), something isn't configured correctly.
Return 0 when on testnet and return 470000 when on mainnet, I guess, but what does in control exactly? Trying to adapt this for another coin and I don't quite understand this part.
Nodes that have blocks less than that number are
discarded by the crawler as not good candidates,
see IsGood db.h:108
Excellent answer, Yarkol. This will be added to the instructions.
Most of the important changes needed are included in the git commit history mentioned above and also in the seeder instructions but this one hasn't been mentioned. It could cause a real pain for devs if the seeder starts kicking nodes at specific blocks, so they should be made aware of this.