Re: [Boost-users] [ASIO] Resolve hostname to IPv4 or IPv6

Subject: Re: [Boost-users] [ASIO] Resolve hostname to IPv4 or IPv6
From: Alexander Lamaison (awl03_at_[hidden])
Date: 2010-05-31 06:57:35

On Sat, 29 May 2010 19:39:50 +0100, Alexander Lamaison wrote:

> I'm trying to add IPv6 support to my program without breaking IPv4.  What
> is the canonical way, if any, to do this win ASIO on Windows.
...

> I originally though that all_matching would mean this code would resolve an
> IPv6 address if necessary but it doesn't.  So I made the following changes:
> 
> 	tcp::resolver resolver(m_io);
> 	typedef tcp::resolver::query Lookup;
> 	Lookup query(
> 		tcp::v6(), host_name, lexical_cast<string>(port), 
> 		Lookup::all_matching | Lookup::v4_mapped |
> 		Lookup::numeric_service);
> 
> This works on my test IPv6 setup but is it good enough?  There are all
> sorts of things I don't understand like mapping and tunnelling so I'm
> looking for a best practice for IP-agnostic name resolution.

Turns  out, this does indeed break IPv4 when run from an OS such as Windows
2000 that doesn't have IPv6.  How can I resolve a hostname in both
situations?

Many thanks.

Alex Lamaison

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