[bittorrent] bittorrent] One connection for download and upload?

Joris Guisson joris.guisson at gmail.com
Fri Nov 3 02:17:13 EST 2006


There is no client which uses 2 connections, you do not have a choice in
this matter, you use one connection per peer. Most clients will probably
refuse a second connection from a peer it is already connected to.

Joris,

On 11/3/06, Yao-Chin Wu <yaochinwu at yahoo.com> wrote:
>
> Thank you for your prompt response.
>
> I have this idea mainly because it is easier to implement. The thread
> handles its own inbound or outbound connection can focus only on its own
> job.

Besides, in typical case, a peer may not always need to send and receive
> data from the same peer. But, it seems like it is not a good idea at all. If
> other members can also provide your opinion, that will also be appreciated.


BTW, Mike mentioned that one connection is the standard in this situation.
> And there is a short paragraphe in Bittorrent protocal, which says,"Peer
> connections are symmetrical. Messages sent in both directions look the same,
> and data can flow in either direction." Does your point come from here? If
> it is the standard, there must be no Bittorrent client designed to use
> separated connections because it could even fail to work with other existing
> implmentation: one peer cannot handle download and upload in one connectoin
> while its uploader assumes it could, and send a request message through this
> connection and would never get response. Thank you.




*Alan McGovern <alan.mcgovern at gmail.com>* wrote:
>
> Hi,
>
> There's no point in not using the same connection to both send and receive
> data. No program that i know of would use a seperate socket to send data and
> receive data from the the same host, it's inefficient and awkward.
>
> Thanks,
> Alan.
>
> (forgot to hit "reply to all" the first time, sorry)
>
>
> On 11/2/06, Michael Parker <mgp at ucla.edu> wrote:
> >
> >
> > On Nov 2, 2006, at 8:22 AM, Yao-Chin Wu wrote:
> > > Dear all,
> > >
> > >     I am a college student and doing a project related to P2P
> > > structure. Bittorrent is a excellent resource for us, and we are
> > > trying to understand its code as much as possible.
> > >
> > >     Accroding to the Bittorrent client implemented by Bram Cohen,
> > > it looks like using only one connection when peer A is downloading
> > > a piece from peer B and peer B also wants to download a piece from
> > > peer A ( one connection for downloading and uploading also). Is
> > > that correct? Is there other implementatioins using seperated
> > > connections for this situation? Which one may be better? Thank you
> > > for your help!
> > >
> >
> > Yes, the standard is that there is only one connection between them.
> > I don't think there's much point to separated connections for
> > uploading and downloading -- by using a single connection you can cut
> > the overhead from the TCP headers in half. Also, if two different
> > connections were used, that gives me the impression that each side is
> > responsible for creating one of the connections (although not
> > necessarily). But with the prevalence of NATs and firewalls today,
> > you'd be running a greater risk of one side not being able to connect
> > at all, and hence one side not being able to download or upload at all.
> >
> > - Mike
> >
> >
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> >
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