Maxime Devos <maximedevos@telenet.be> writes:

> Maybe the IPV6_V6ONLY (see the ipv6(7) man page) is relevant here.
> Alternatively, you could run two servers in parallel: one bound to an
> IPv4 address and another bound to an IPv6 address.

My feeling is that IPV6_ONLY is best avoided, for portability, and
because mapped addresses (an IPv6 address with the v4 address embedded)
are awkward.    So I think it's best to listen on v4 and v6 separately.