When you create an ipv6 listening socket in mIRC, TCP or UDP, at the lower level in winsock, there is a member in a structure that's always on by default on Windows: IPV6_V6ONLY
This parameter means that for an ipv6 socket, by default, it will only accept/connect to ipv6 connections/server, this is not great in many cases (that parameter can be found off by default on different OS).
For example, creating a game server which has to accept anyone, so any version of ip.
If this option is turned off, ipv4 connection should be able to connect to ipv6 server, the ipv4 will be mapped to some ipv6 addresses.
In fact it looks like this also works for ipv6 client to ipv4 server.
I would like to get support for this via some switch in /socklisten, /sockudp -k and eventually /sockopen but i'm really looking for the server side of ithttps://docs.microsoft.com/en-us/windows/win32/winsock/dual-stack-sockets