What is a .torrent file?

The ".torrent" file is a BT seed file; the file in this format is defined by the BitTorrent protocol. The seed file of the BitTorrent protocol can save the metadata of a set of files and contains the file information necessary for BT downloading, bt The role of seeds is equivalent to URL links in HTTP downloads.

The operating environment of this tutorial: Windows 10 system, DELL G3 computer.

What is a .torrent file?

The seed file (English: Torrent file) of the BitTorrent protocol can save the metadata of a set of files. Files in this format are defined by the BitTorrent protocol. The extension is generally ".torrent".

Torrent is the suffix name of BT seed file. It is a computer file with a general size of about 10-500KB.

The file contains the file information necessary for BT download. The function of bt seed is equivalent to the URL connection in HTTP download.

BitTorrent (BT), the biggest feature and advantage is the use of "Multi-source File Transmission Protocol (MFTP, Multi-source File Transmission Protocol)". The word actually comes from eDonkey's protocol documentation, but it was used earlier and more maturely on BT. The principles of BT and eDonkey are exactly the same. They both cut a file into several file pieces (Pieces) and mark each piece with a special mark. The size of a general file piece is 256K bytes or 512K bytes. When downloading, the user does not download the complete file from a fixed node (such as the central server of a traditional network or the node where the file is initially searched), but downloads different files from multiple nodes that hold part or all of the file at the same time. film, and finally get the complete file. Because the file is fragmented, it can support resumed downloads. At the same time, after each node obtains a file piece, it can upload it to other nodes. This reduces the pressure on the server or the node that originally owned the file, and the upload service is distributed to all nodes participating in the download.

There is a central server Tracker in BT's network architecture, which is used to save the IP address and port information of each node in the BT network. When the download node first joins the network, it obtains the address information of other nodes from Trakcer. In addition, BT is different from common P2P networks in that its functions are mainly limited to the file transfer process, while the release and query of shared files are implemented through the Web server. When downloading a BT node, you must first download a file with a .torrent extension from the Web server through a simple HTTP protocol. The node then connects to the Tracker server using the HTTP protocol through the information contained in the .torrent file. The Tracker server records the file information requested by the node to download as well as the node's IP address and port number, and replies to the node with a randomly generated list of nodes that download the file. The download node establishes a connection with the nodes on the list to realize multi-source downloading. When the downloader has the complete file, it is called a "seed". BT's network architecture is shown in the figure.

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