MC-3776 (IPv6 Does Not Work) is marked as fixed, so I went to test out Minecraft between two IPv6-only hosts. While it is possible to connect to another multiplayer session over IPv6 by entering the IPv6 address manually in the "server address" box of the "direct connect" UI screen (you have to remember to enclose the IPv6 address in square brackets so the port number can be distinguished from the IP address segments delimited by colons (what are these called? IPv4 called the octets, since they were 8bits. So hexidectets for IPv6? Ed: sources suggest "hextet", "hexadectet", "hexadecatet", "quibble", "quartet", or "piece")).
But IPv4 multiplayer servers on your LAN show up automatically under your list of multiplayer servers, so the kids can connect without manually entering IP addresses. This functionality should also work with IPv6.
Note that while it is possible to play multiplayer over IPv6, you still have to be dual stack, because IPv4 is required to download the jar files (MCL-2627 Launcher will not download game over IPv6) and to authenticate to Mojang
This may be a manifestation or consequence of MC-98598 "LAN List does not populate reliably"
- On server machine, turn off IPv4 (eg on MacOS, go to System Preferences -> Network -> Advanced -> TCP/IP -> Configure IPv4 = Off), but ensure that IPv6 is enabled and addressable.
- On client machine, turn off IPv4 as well, and IPv6 is enabled. Both hosts are now IPv6-only single stack hosts.
- On server machine, launch Minecraft session, enter a Minecraft world, hit escape to pause, and choose "Open to LAN" -> "Start LAN World"
- On client machine, choose "Multiplayer" from the title screen
- Server machine session is seen at the bottom "local network" section of the "Play Multiplayer" server list
→ Note that if the session does show up, you might be able to connect at a low level, but you wouldn't be able to authenticate on an IPv6-only host, so you would not successfully join the session until WEB-197 is fixed. This report is only about populating LAN list, not connecting/authenticating.
- Server session is not seen