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My sister and I have been playing Minecraft LAN together easily for the last six months. And then suddenly a week ago, it just stopped working. Anytime we try to connect, we get the message: "Connection timed out; no further information."
We don't know what has happened. It was working fine, until it wasn't. I've looked at over 20 different forums and help sites, and I've even tried just trying out my own solutions. Nothing has worked. We're on the same network, in the same room, different player names, Java can get through our firewall, we're on the same version, we're both playing vanilla Minecraft, and we don't know what's gone wrong. All of the forums I've looked at have all just been stuff like "Me too!" or "Have you solved it yet?" or "Woopsie! It couldn't get through our firewall! Thanks!"... Nothing useful to our situation.