Using DHT  Requires libTorrent/rTorrent version 0.12.0/0.8.0 or
higher (or SVN revision 1013).  The distributed hash table (DHT)
is a feature that acts as backup tracker when all other trackers
are down or can't deliver enough peers, as well as enabling
trackerless torrents.   You must have set a session directory to
use DHT.  From the sample .rtorrent.rc:  # dht = auto  # UDP
port to use for DHT.  # dht_port = 6881  If "dht" is not set to
"disable", torrents that aren't private automatically get a DHT
backup tracker added to the tracker list. This pseudo-tracker is
used whenever all regular trackers are down, disabled, or don't
deliver enough peers, to find additional peers from the
distributed hash table and to allow other peers to find us.
When starting a torrent with a DHT tracker (or when starting
rtorrent if "dht" is "on"), you will see the log message
"Starting DHT server on port ###". If an error occurs while
starting the DHT server (e.g. the UDP port is already in use or
invalid), "dht" is set to "o