- Distributed Hash Table (DHT)
- A decentralized, distributed database containing file info hashes with associated lists of active peer IPs, distributed across many nodes.
- Downloader
- A peer, connected to a swarm, who does not have a complete copy of the file.
- File Sharing
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The exchange of media and software, passed through a centralized server (such as FTP, email, and instant messaging), distributed cloud storage (such as Dropbox, Google Drive, and Microsoft OneDrive), or direct peer-to-peer channels (such as BitTorrent and Gnutella).
- Leech
- A peer that downloads content, but does not upload it in return to the swarm.
- Node
- Packaged with every file sharing client is another client/server application which communicates over UDP with other nodes to update the active list of peers by using a DHT.
- Peer
- Anyone participating in file sharing, whether they are a seed or a downloader.
- Seed
- Someone with a complete copy of some content, who stays online to share the file with others.
- Swarm
- A group of peers sharing a file.
- Torrent
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A BitTorrent file is an inventory list (metadata) of content to share (music, video, etc) -- it only has information about those files (sizes, names), as well as other metadata (content category, name of the BitTorrent file). Each BitTorrent file has a unique global identifier called an “info hash,” which is a hexadecimal number generated from evaluating its metadata and associated content.
- Tracker
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A website that hosts a list of files or self-contained data in a long URL (like a magnet). These do not contain any file data, but instead a list of peers that may contain the data.
Sites like Pirate Bay do not have file data. It’s an index of .torrent files (or magnet URI) with information about IP addresses of peers and ports to connect to. Connecting to those peers will allow to ask for more peers. Tracker events are then BitTorrents that are discovering peers. Torrent peer lists are usually self-updating.
At least 1 peer, that knows where to connect and discover peers, is necessary to get the data. The tracker approaches the first peer and asks, “Do you know anyone else?” From that peer, the protocol repeats the process with other peers to find more peers with more data.
Glossary of Terms - File Sharing
