This is mostly me being salty because my router (not in my control atm)/ISP sucks and keeps dropping IPv4 connections for no reason, and so I keep on disconnecting from Royals. But it would be excellent if the MapleRoyals client and server used IPv6 because for whatever reason my router/ISP is happy to keep those connections going.
While technically possible, the amount of work required to allow IPv6 connections, not to mention the major implications it can or will have to some aspects of the game or TOS (OTOMH server connections, bans, votes), it is not something we plan to work on in the near future. IPv4 still 'rules' the internet, but IPv6 has steadily been gaining traction over the past years, so maybe a few years in the future when IPv6 connections becomes a viable alternative for all internet connections around the world, we might revisit this suggestion, but right now it's just too niche a feature to work on, albeit (IMO) an awesome suggestion.
