µTP header

[sangeeta]

From last one week I am trying to decode µTP header, but till now did not get the sufficient information.

I disabled DHT and download one file over µTorrent from same client.

The first header which I received with protocol name as - BT DHT

0000 44 37 e6 63 cb c2 60 eb 69 ec 68 2f 08 00 45 00 D7.c..`. i.h/..E.

0010 00 83 4c 34 00 00 40 11 ba 74 ac 13 0e 4f ac 13 ..L4..@. .t...O..

0020 0d 4c 76 cd 78 31 00 6f 7f c8 64 31 3a 61 64 32 .Lv.x1.o ..d1:ad2

0030 3a 69 64 32 30 3a 25 46 80 de ac 9e b4 04 99 f2 :id20:%F ........

0040 df 11 52 46 0a 31 af 22 28 bb 36 3a 74 61 72 67 ..RF.1." (.6:targ

0050 65 74 32 30 3a f7 75 d8 a3 2e 5b 74 c4 e0 ef 3e et20:.u. ..[t...>

0060 6c 55 46 96 38 a0 15 1f c8 65 31 3a 71 39 3a 66 lUF.8... .e1:q9:f

0070 69 6e 64 5f 6e 6f 64 65 31 3a 74 34 3a e0 d1 86 ind_node 1:t4:...

0080 10 31 3a 76 34 3a 55 54 68 1a 31 3a 79 31 3a 71 .1:v4:UT h.1:y1:q

0090 65 e

This is the request for DHT

I am not able to understand what all these hex code saying

Next, TCP and BitTorrent handshake takes place

Next packet info in wireshark says

"BitTorrent 164 Extended"

What does it mean?

Corresponding header for this is

0000 60 eb 69 ec 68 2f 44 37 e6 63 cb c2 08 00 45 00 `.i.h/D7 .c....E.

0010 00 96 74 ee 40 00 80 06 11 b2 ac 13 0d 4c ac 13 ..t.@... .....L..

0020 0e 4f ff 2d 76 cd 5f e5 3d 3e e6 c0 11 ac 50 18 .O.-v._. =>....P.

0030 03 ce 74 4a 00 00 63 6f 6d 6d 65 6e 64 69 35 65 ..tJ..co mmendi5e

0040 31 30 3a 75 74 5f 63 6f 6d 6d 65 6e 74 69 36 65 10:ut_co mmenti6e

0050 65 31 33 3a 6d 65 74 61 64 61 74 61 5f 73 69 7a e13:meta data_siz

0060 65 69 31 30 38 35 39 65 31 3a 70 69 33 30 37 36 ei10859e 1:pi3076

0070 39 65 34 3a 72 65 71 71 69 32 35 35 65 31 3a 76 9e4:reqq i255e1:v

0080 31 33 3a c2 b5 54 6f 72 72 65 6e 74 20 33 2e 31 13:..Tor rent 3.1

0090 36 3a 79 6f 75 72 69 70 34 3a ac 13 0e 4f 65 00 6:yourip 4:...Oe.

00a0 00 00 01 0f ....

Please help me to decode each bit of this header.

[schnurlos]

This could be a help:

http://www.utorrent.com/help/documentation/utp and

http://bittorrent.org/beps/bep_0029.html#extension

[sangeeta]

Thanks

[sangeeta]

I want to know one more thing,

if peer requests for some file, it will get some pieces from some other peer and some pieces from another peers, now how will requesting peer tell that which piece is required by it?

Where it is mentioned?

How responding peer will come to know, which piece should I send?

After uTP header, data payload starts or their is some information regarding piece like piece length,piece no, etc?

[Firon]

Go read the BitTorrent specification.