mldonkey is kind of a special beast among P2P file sharing software in that it is basically a headless server, with GUIs being more or less an after-thought that in my experience do not really work. I started using mldonkey because I was specifically looking for headless software to run on the Donkey and Kademlia networks, and have found it quite simple to operate from a telnet command line.
Defaults are all quite sane except that Kad is turned off by default, ie. this setting must be changed in downloads.ini:
enable_kademlia = true
Connect to and control mldonkey thusly:
telnet localhost 4000
auth admin ""
where "mlnet" starts the mldonkey server, and the "auth" line logs in to the server. At the admin prompt, here are a subset of commands that I personally find useful:
start download: dllink view download status: vd list connected servers: vm list server id assignment: id kad_boot 188.8.131.52 4166 kad_dump_known_peers kad_stats kad_load : load the peers from a contact.dat file search: s view all queries: vs view results: vr download search result: dd exit: q stop server: kill