Turn off IPV6_V6ONLY or two listening sockets

Question

Is it better to have two listening sockets one ipv4 and one ipv6 or to have one ipv6 socket that has had ipv6 only turned off. I would like to support both ipv4 and ipv6 from the start so I don't want to have to redo it later and have it hacked together. From what I can tell there isn't any problems with having ipv6 only turned off but I don't have much experience in dealing with ipv6 networking. What may or may not go wrong with this problem.

Answer 1

There are operating system out there which just don't support providing both protocols over the same socket. There you can switch off IPV6_V6ONLY as much as you want, it will have no effect.

If you want to stay compatible with these systems - Windows XP is an example - you'll have to work with two sockets.