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{-# LANGUAGE OverloadedStrings #-}
module Network.Torrent.Handshake
( Handshake
, defaultProtocol, defaultReserved, defaultHandshake
) where
import Control.Applicative
import Data.Word
import Data.ByteString (ByteString)
import qualified Data.ByteString as B
import Data.Serialize
import Network.Torrent.PeerID
-- | In order to establish the connection between peers we should send 'Handshake'
-- message. The 'Handshake' is a required message and must be the first message
-- transmitted by the peer to the another peer.
data Handshake = Handshake {
hsProtocol :: ByteString -- ^ Identifier of the protocol.
, hsReserved :: Word64 -- ^ Reserved bytes, rarely used.
, hsInfoHash :: ByteString -- ^ Hash from the metainfo file.
-- This /should be/ same hash that is transmitted in tracker requests.
, hsPeerID :: PeerID -- ^ Peer id of the initiator.
-- This is /usually the same peer id that is transmitted in tracker requests.
} deriving (Show, Eq)
instance Serialize Handshake where
put hs = do
putWord8 (49 + fromIntegral (B.length (hsProtocol hs)))
putByteString (hsProtocol hs)
putWord64be (hsReserved hs)
putByteString (hsInfoHash hs)
put (hsPeerID hs)
get = do
len <- getWord8
Handshake <$> getBytes (fromIntegral len)
<*> getWord64be
<*> getBytes 20
<*> get
-- | Default protocol string "BitTorrent protocol" as is.
defaultProtocol :: ByteString
defaultProtocol = "BitTorrent protocol"
-- | Default reserved word is 0.
defaultReserved :: Word64
defaultReserved = 0
-- | Length of info hash and peer id is unchecked, so it /should/ be equal 20.
defaultHandshake :: ByteString -- ^ Info hash string.
-> PeerID
-> Handshake
defaultHandshake hash pid = Handshake defaultProtocol defaultReserved hash pid
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