An implementation of Bittorent DHT (BEP-0005)
http://www.bittorrent.org/beps/bep_0005.html

Each node in the network chooses an arbitrary 160 bit unique
ID, and maintains a list of nodes which is distributed based
on an XOR distance metric to be denser closer to its own ID. 
Each node also maintains a table mapping 160 bit bittorrent
info_hashes to peer addresses. When a client wants to lookup
a torrent, it asks the nodes in its table closest to the
torrent's info_hash, who will either respond with their
table entries, or with a set of closer nodes. Once a node
with table entries is found, or if there are no closer nodes
to ask, the client gives the closet nodes its address.