Lancast allows clients in the same LAN (or VPN) to share their files at a very high speed, providing them with the ability of finding sources and files (keyword searches are available only on Lancast version 2; the first version of Lancast looks for ed2k hashes only) inside their LAN or VPN.
Lancast does not require an ed2k server and does not implement a LAN/VPN implementation of Kad network. Lancast relies on UDP multicasting (and thus may require IGMP support in the LAN or VPN where the clients reside; people may use UDP multicast streaming features of the VLC media player to find out whether multicasting works in their net).
It is a common misconception that Lancast uses UDP multicasting also for file transfer. In fact, it doesn't! Files are served over regular (unicast) connections.
For file transfer a modified Upload Bandwidth Throttler is used which provides a separate upload limit for LAN/VPN clients. Simpler implementations of Lancast use just unlimited upload.
Lancast is not usable over the Internet since multicast is disabled by 99,9% of all providers (except MBONE) and because Lancast wouldn't bring any speed advantages over ed2k/Kad anyway.
The Lancast feature is currently available in the following mods:
- Lancast version 2 — in NeoMule since v4.x,
- Lancast version 1 — in eMule Plus and Sivka. (Lancast was orginally written by moosetea and posted as a patch, I should know because I'm moosetea and I worked on the Emule Plus project in 2003/2004ish :P)
Lancast is also in the «to do list» of features for the MorphXT, but is not likely to be implemented soon.
Since Webcache has become criticized and abandoned, the Lancast feature now remains as one of the most advantageous tools allowing for Internet providers to economize their external traffic. By promoting the use of Lancast-capable mods of eMule in LANs and/or VPNs, all the file exchange ed2k/Kad traffic between the clients of the same provider becomes local (otherwise the traffic would twice traverse the local/Internet boundary).
 Comparison with μTorrent
According to μTorrent help file (Appendix A, «Preferences» section, «BitTorrent» subsection), μTorrent has a similar feature called Enable Local Peer Discovery:
- Enable Local Peer Discovery allows µTorrent to attempt to discover local peers via multicast. If a peer is considered local, transfer rates with the peer will not be limited unless Limit local peer bandwidth is also enabled. Local Peer Discovery will not be used for .torrent files with the 'private' flag set.