CODEWITHSUNDEEP
bittorrent
osa1
osa1

Reputation: 7078

BitTorrent protocol can't get answers to my piece requests

I'm developing a BitTorrent client and I'm having trouble getting answers to my piece requests.

To debug, I followed a conversation between uTorrent and transmission using Wireshark and tried to imitate same conversation in my client. But it still doesn't work.

Below is an example conversation happening between my client and transmission. (my client also using -TR--- prefixed peer id, this is only for testing purposes and I'll change this)

Indented messages are coming from transmission, others are messages my client send.

Note that this conversation is not exactly same as how uTorrent and transmission would talk, because my client does not support fast extension yet. (BEP 6)

(Output is taken from Wireshark, lines starting with -- are my comments)

00000000  13 42 69 74 54 6f 72 72  65 6e 74 20 70 72 6f 74 .BitTorr ent prot

00000010  6f 63 6f 6c 00 00 00 00  00 10 00 00 f8 9e 0d fd ocol.... ........

00000020  9c fc a8 52 d9 7a d6 af  a4 4d 8f 73 ce 70 b6 36 ...R.z.. .M.s.p.6

00000030  2d 54 52 32 38 34 30 2d  36 68 61 67 76 30 73 70 -TR2840- 6hagv0sp

00000040  34 67 37 6b                                      4g7k
-- ^ my handshake to transmission

    00000000  13 42 69 74 54 6f 72 72  65 6e 74 20 70 72 6f 74 .BitTorr ent prot

    00000010  6f 63 6f 6c 00 00 00 00  00 10 00 04 f8 9e 0d fd ocol.... ........

    00000020  9c fc a8 52 d9 7a d6 af  a4 4d 8f 73 ce 70 b6 36 ...R.z.. .M.s.p.6

    00000030  2d 54 52 32 38 34 30 2d  72 73 35 68 71 67 32 68 -TR2840- rs5hqg2h

    00000040  6e 70 68 64                                      nphd
    -- ^ transmission answers to my handshake

00000044  00 00 00 1a 14 00 64 31  3a 6d 64 31 31 3a 75 74 ......d1 :md11:ut

00000054  5f 6d 65 74 61 64 61 74  61 69 33 65 65 65       _metadat ai3eee
    -- ^ my extended handshake to transmission

    00000044  00 00 00 72 14 00 64 31  3a 65 69 31 65 31 3a 6d ...r..d1 :ei1e1:m

    00000054  64 31 31 3a 75 74 5f 6d  65 74 61 64 61 74 61 69 d11:ut_m etadatai

    00000064  33 65 65 31 33 3a 6d 65  74 61 64 61 74 61 5f 73 3ee13:me tadata_s

    00000074  69 7a 65 69 31 34 37 65  31 3a 70 69 35 31 34 31 izei147e 1:pi5141

    00000084  33 65 34 3a 72 65 71 71  69 35 31 32 65 31 31 3a 3e4:reqq i512e11:

    00000094  75 70 6c 6f 61 64 5f 6f  6e 6c 79 69 31 65 31 3a upload_o nlyi1e1:

    000000A4  76 31 37 3a 54 72 61 6e  73 6d 69 73 73 69 6f 6e v17:Tran smission

    000000B4  20 32 2e 38 34 65 00 00  00 02 05 80              2.84e.. ....
    -- ^ transmission's extended handshake and bitfield

    000000C0  00 00 00 01 01                                   .....
    -- ^ transmission unchokes me

00000062  00 00 00 01 02                                   .....
-- ^ my interested message

00000067  00 00 00 0d 06 00 00 00  00 00 00 00 00 00 00 40 ........ .......@

00000077  00                                               .
-- ^ piece request

-- no answers ...

00000078  00 00 00 0d 06 00 00 00  00 00 00 00 00 00 00 40 ........ .......@

00000088  00                                               .
-- ^ piece request again, with 10 seconds interval

-- again no answers...

00000089  00 00 00 0d 06 00 00 00  00 00 00 00 00 00 00 40 ........ .......@

00000099  00                                               .
-- ^ piece request again, with 10 seconds interval

-- no answers...

Any ideas what am I doing wrong?

Thanks.

EDIT: I updated my client to send unchoke just after sending interested, but I'm still having same problem...

Upvotes: 0

Views: 575

Answers (1)

osa1
osa1

Reputation: 7078

The problem was that I was requesting a piece bigger than the total size of the torrent.

The torrent I was using has 2 files, in total of 12KB. However the piece size of the torrent is 16KB and I was requesting 16KB piece even though the torrent file has only one piece and it's 12 KB in total.

After requesting 12KB instead of 16KB, the problem was solved.

Upvotes: 3

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