Super janky download first piece

p2p/p2p.go

@@ -1,8 +1,15 @@
 package p2p
 
 import (
+	"crypto/sha1"
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"math"
 	"net"
 	"strconv"
+
+	"github.com/veggiedefender/torrent-client/message"
 )
 
 // Peer encodes connection information for a peer
@@ -14,16 +21,74 @@ type Peer struct {
 // Downloader holds data required to download a torrent from a list of peers
 type Downloader struct {
 	Peers       []Peer
+	PeerID      [20]byte
 	InfoHash    [20]byte
+	PieceHashes [][20]byte
 	Length      int
 }
 
 // Download downloads a torrent
 func (d *Downloader) Download() error {
+	conn, err := d.Peers[0].connect(d.PeerID, d.InfoHash)
+	defer conn.Close()
+	if err != nil {
+		return err
+	}
+	_, err = d.handshake(conn)
+	if err != nil {
+		return err
+	}
+
+	choked := false
+	pieceSize := d.Length / len(d.PieceHashes)
+	buf := make([]byte, pieceSize)
+	i := 0
+	for i < pieceSize {
+		msg, err := message.ReadMessage(conn)
+		if err != nil {
+			return err
+		}
+
+		switch msg.ID {
+		case message.MsgChoke:
+			choked = true
+		case message.MsgUnchoke:
+			choked = false
+		case message.MsgPiece:
+			begin := binary.BigEndian.Uint32(msg.Payload[4:8])
+			copy(buf[begin:], msg.Payload[8:])
+			i += (len(msg.Payload) - 8)
+		}
+
+		if !choked {
+			index := 0 // Piece number
+			begin := i // Offset
+			remain := pieceSize - i
+			length := int(math.Min(float64(16384), float64(pieceSize)))
+			length = int(math.Min(float64(remain), float64(length)))
+			payload := make([]byte, 12)
+			binary.BigEndian.PutUint32(payload[0:4], uint32(index))
+			binary.BigEndian.PutUint32(payload[4:8], uint32(begin))
+			binary.BigEndian.PutUint32(payload[8:12], uint32(length))
+			request := message.Message{
+				ID:      message.MsgRequest,
+				Payload: payload,
+			}
+			_, err := conn.Write(request.Serialize())
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	s := sha1.Sum(buf)
+	fmt.Println(hex.EncodeToString(s[:]))
+	fmt.Println(hex.EncodeToString(d.PieceHashes[0][:]))
+
 	return nil
 }
 
-func connect(p *Peer, peerID [20]byte, infoHash [20]byte) (net.Conn, error) {
+func (p *Peer) connect(peerID [20]byte, infoHash [20]byte) (net.Conn, error) {
 	hostPort := net.JoinHostPort(p.IP.String(), strconv.Itoa(int(p.Port)))
 	conn, err := net.Dial("tcp", hostPort)
 	if err != nil {
@@ -31,3 +96,21 @@ func connect(p *Peer, peerID [20]byte, infoHash [20]byte) (net.Conn, error) {
 	}
 	return conn, nil
 }
+
+func (d *Downloader) handshake(conn net.Conn) (*message.Handshake, error) {
+	req := message.Handshake{
+		Pstr:     "BitTorrent protocol",
+		InfoHash: d.InfoHash,
+		PeerID:   d.PeerID,
+	}
+	_, err := conn.Write(req.Serialize())
+	if err != nil {
+		return nil, err
+	}
+
+	res, err := message.ReadHandshake(conn)
+	if err != nil {
+		return nil, err
+	}
+	return res, nil
+}

torrent/torrent.go

@@ -50,7 +50,9 @@ func (t *Torrent) Download() error {
 	peers := []p2p.Peer{{IP: net.IP{127, 0, 0, 1}, Port: 51413}}
 	downloader := p2p.Downloader{
 		Peers:       peers,
+		PeerID:      peerID,
 		InfoHash:    t.InfoHash,
+		PieceHashes: t.PieceHashes,
 		Length:      t.Length,
 	}
 	err = downloader.Download()