From: "Luis G." <l17339@...>
Date: 2010-12-16T23:49:44+09:00
Subject: Re: How to do UDP calls

Maybe I have not explained well...

I'm basically sending requests to torrent trackers to get the number of 
seeds and peers of a torrent in a specific tracker.
As you might know, you can have this:

http://9.rarbg.com:2710/announce
udp://tracker.openbittorrent.com:80/announce

so, you can have http and udp trackers.

For the first one (HTTP) I just use this:

url = tracker_url + 
'?info_hash=%19%89B%0AL%87k%9A%2B%28%3A%B36%9D%93%9A%8D%FA%97I'

agent = Mechanize.new do |a|
      a.history.max_size = 1
      a.read_timeout = 60
end

res = agent.get(url).save_as(path)

with this I get a file with the number of seeds and peers on it. I just 
need to open the file in 'path' and extract the information.

But for the second one (UDP) I can't use Mechanize, so I need to work 
with the standard library as you told before.

I never used socket library before, so I'm kinda lost.
I was trying something like:

host = 'tracker.openbittorrent.com'
port = 80
data = '%19%89B%0AL%87k%9A%2B%28%3A%B36%9D%93%9A%8D%FA%97I'

sock = UDPSocket.open
sock.connect(host, port)
sock.send("?info_hash=" + data, 0)

But there are some things here that I don't know:

1- The main idea is to create a socket, connect it to the remote host, 
send the request and get the response, right?

2- do I need to include the 'udp://' in the host?

3- is ok to include the name of the field I want to send (?info_hash=) 
in the data variable? I need to include that as you can see here: 
http://wiki.theory.org/BitTorrent_Tracker_Protocol

4- how can I get the response from the server? something like: 
sock.recvfrom(1024)?

I tried several options and I had no success.

Any clues?

Thanks,

Luis

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