From: Matt Whitlock <bip@mattwhitlock.name>
To: Jim Phillips <jim@ergophobia.org>
Date: Tue, 26 May 2015 00:52:07 -0400
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Zero-Conf for Full Node Discovery
Precedence: list

On Monday, 25 May 2015, at 11:48 pm, Jim Phillips wrote:
> Do any wallets actually do this yet?

Not that I know of, but they do seed their address database via DNS, which you can poison if you control the LAN's DNS resolver. I did this for a Bitcoin-only Wi-Fi network I operated at a remote festival. We had well over a hundred lightweight wallets, all trying to connect to the Bitcoin P2P network over a very bandwidth-constrained Internet link, so I poisoned the DNS and rejected all outbound connection attempts on port 8333, to force all the wallets to connect to a single local full node, which had connectivity to a single remote node over the Internet. Thus, all the lightweight wallets at the festival had Bitcoin network connectivity, but we only needed to backhaul the Bitcoin network's transaction traffic once.


> On May 25, 2015 11:37 PM, "Matt Whitlock" <bip@mattwhitlock.name> wrote:
> 
> > This is very simple to do. Just ping the "all nodes" address (ff02::1) and
> > try connecting to TCP port 8333 of each node that responds. Shouldn't take
> > but more than a few milliseconds on any but the most densely populated LANs.
> >
> >
> > On Monday, 25 May 2015, at 11:06 pm, Jim Phillips wrote:
> > > Is there any work being done on using some kind of zero-conf service
> > > discovery protocol so that lightweight clients can find a full node on
> > the
> > > same LAN to peer with rather than having to tie up WAN bandwidth?
> > >
> > > I envision a future where lightweight devices within a home use SPV over
> > > WiFi to connect with a home server which in turn relays the transactions
> > > they create out to the larger and faster relays on the Internet.
> > >
> > > In a situation where there are hundreds or thousands of small SPV devices
> > > in a single home (if 21, Inc. is successful) monitoring the blockchain,
> > > this could result in lower traffic across the slow WAN connection.  And
> > > yes, I realize it could potentially take a LOT of these devices before
> > the
> > > total bandwidth is greater than downloading a full copy of the
> > blockchain,
> > > but there's other reasons to host your own full node -- trust being one.
> > >
> > > --
> > > *James G. Phillips IV*
> > > <https://plus.google.com/u/0/113107039501292625391/posts>
> > > <http://www.linkedin.com/in/ergophobe>
> > >
> > > *"Don't bunt. Aim out of the ball park. Aim for the company of
> > immortals."
> > > -- David Ogilvy*
> > >
> > >  *This message was created with 100% recycled electrons. Please think
> > twice
> > > before printing.*
> >