Торрент-файл - это специально форматированный двоичный файл. Он всегда содержит список файлов и метаданных целостности обо всех частях и, возможно, содержит список трекеров.
торрент-файл является bencoded словарь со следующими ключами:
announce - the URL of the tracker
info - this maps to a dictionary whose keys are dependent on whether one or more files are being shared:
name - suggested file/directory name where the file(s) is/are to be saved
piece length - number of bytes per piece. This is commonly 28KiB = 256 KiB = 262,144 B.
pieces - a hash list. That is, a concatenation of each piece's SHA-1 hash. As SHA-1 returns a 160-bit hash, pieces will be a string whose length is a multiple of 160-bits.
length - size of the file in bytes (only when one file is being shared)
files - a list of dictionaries each corresponding to a file (only when multiple files are being shared). Each dictionary has the following keys:
path - a list of strings corresponding to subdirectory names, the last of which is the actual file name
length - size of the file in bytes.
http://en.wikipedia.org/wiki/Torrent_file#File_structure – SLaks