From: "Luis G." <l17339@...>
Date: 2010-12-20T19:40:31+09:00
Subject: Re: How to do UDP calls

Hello again.

Thanks for your explanation.
I understood that we need to split a 64bit integer in two 32 bit integer 
and pack them in network-byte order.
So, as you said:

connection_id = 0x41727101980
pp connection_id
>> 4497486125440

s = [connection_id >> 32, connection_id & 0xffffffff, 0, 
16].pack('NNNN')
c0, c1, action, trans_id = s.unpack("NNNN")
conn = (c0 << 32) | c1

pp conn
>> 4497486125440

pp action
>> 0

pp trans_id
>> 16

I did this small test like you explained and I get the same values after 
pack and unpack the information(connection_id = conn).

So, after I pack the data, I send it and I get a response:

sock = UDPSocket.open
sock.connect(host, port)
sock.send(s, 0)
response = sock.recvfrom(1024)

so, I extract the content of the response like this (using a different 
order of the request):

action, trans_id, c0, c1 = response[0].unpack("NNNN")
conn_id = (c0 << 32) | c1

pp action
>> 0

pp trans_id
>> 16

pp conn_id
>> 2540598739861590271

In the documentation says:
- Check whether the transaction ID is equal to the one you choose - I 
got the same value '16', so I think is ok;
- Check whether the action is connect - I got a '0'... Shouldn't I get a 
'1'?

The next step is to fill the announce input and send it, so I can get 
the seeds and peers (my goal :)).
I have one question here: All the fields are required, right? Because I 
don't really know some fields, like: peer_id, downloaded, left, 
uploaded, event, key. the field key, for example don't even appear in 
BitTorrent Tracker Protocol 
(http://wiki.theory.org/BitTorrent_Tracker_Protocol)

Just one more question... The info_hash is a 20-byte string. To pack 
this variable, I can use the 'm' flag, right?

Thanks,

Luis Goncalves

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