The Local Peer Discovery protocol, specified as BEP-14,[1] is an extension to the BitTorrent file-distribution system.
It is designed to support the discovery of local BitTorrent peers, aiming to minimize the traffic through the Internet service provider's (ISP) channel and maximize use of higher-bandwidth local area networks (LANs).
Local Peer Discovery is implemented[2] with HTTP-like messages on User Datagram Protocol (UDP) multicast group 239.192.152.143:6771 (IPv4) or ff15::efc0:988f (IPv6)[1] which are administratively scoped multicast addresses.
It's similar to Simple Service Discovery Protocol but sends BT-SEARCH instead of M-SEARCH:
An alternative multicast peer discovery protocol based on ZeroConf is published as BEP 26 Zeroconf Peer Advertising and Discovery, but is not widely adopted since it is considered too complex[9] in comparison.