1 files changed, 38 insertions, 9 deletions

diff --git a/src/Network/Torrent/Handshake.hs b/src/Network/Torrent/Handshake.hs
index d48d04e6..7643b2e9 100644
--- a/src/Network/Torrent/Handshake.hs
+++ b/src/Network/Torrent/Handshake.hs
@@ -1,25 +1,54 @@
 {-# 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
-  , hsReserved    :: Word64
-  , hsInfoHash    :: ByteString
-  , hsPeerID      :: ByteString
+    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
 
-fromByteString :: ByteString -> Handshake
-fromByteString = undefined
-
-toByteString :: Handshake -> ByteString
-toByteString = undefined
\ No newline at end of file
+-- | 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
\ No newline at end of file