Resolving Minecraft 1.12.2 connectivity problems

Minecraft was auto-updated to version 1.12.2 yesterday and it was a great tragedy for the kids who were at home on summer vacations, while I was still at work, since after upgrade local LAN multiplayer did not work, and neither could they start the Minecraft server.

As it turns out the error was quite simple once you found it. The installer updated the game fine, but the Windows Firewall rules were not updated properly. I’d guess it’s because the kids are not using admin accounts on their computers.

On the first computer, the Windows Firewall rules were added for

…\minecraft\runtime\jre-x64\1.8.0_51\bin\javaw.exe and
…\minecraft\runtime\jre-x64\1.8.0_51\bin\java.exe,
but only enabled for java.exe, not for javaw.exe.

On the second computer, there was only added a rule for

…\minecraft\runtime\jre-x64\1.8.0_51\bin\javaw.exe, but it wasn’t enabled.

(I assume the difference comes from the first computer also running the Minecraft server.)

Additionally, the firewall rules for the old version,

…\minecraft\runtime\jre-x64\1.8.0_25\bin\java.exe and
…\minecraft\runtime\jre-x64\1.8.0_25\bin\javaw.exe, were left still enabled.

Cleaning up the rules solved the problems of peer-to-peer play. Updating the connection info to the Minecraft server to its new IP-adress, plus updating the launch path for java.exe solved the remaining glitch.

The world can start turning again for the kids.

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Now uninstalling Java

I finally got a good reason to uninstall Java, rather than just accepting the security updates and installing a new version.

By accident I missed the fine print and didn’t remove that annoying checkbox that allowed Java to install some toolbar into my browsers, both IE and Firefox were quickly infected, and the antivirus program did not respond or think this worth taking action on.

So I had to spend half an hour cleaning out Yahoo-extensions from almost everywhere on the computer: in IE, in Firefox, in Windows Programs, on the disk itself, since uninstallation obviously wasn’t enough to get rid of everything completely.

That kind of did it, I’m not really sure if anything will break due to this, but I’m now removing Java permanently.