Reference -> https://mojang.atlassian.net/browse/MC-15058
With a 1.5.1 world save, the new snapshot will not allow any players into the game, offering a simple "End of stream" when attempting to log in.
However, when using a brand new world save, generated by the snapshot, the end of stream doesn't occur. Therefore I can reason that it must not be something present in anything 1.5.1 or before.
Let's bear in mind that this world save has existed since the early 12w snapshots, so it's nothing with the save itself.
This issue was marked as fixed, but it most certainly is still an issue.
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I can confirm, but I'm nearly certain that it's related to the scoreboard.dat in the data file. Deleting that file got rid of the problem for me.
I'll try that.
It did indeed work. By deleting the scoreboard.dat file, there are no issues logging in.
Cannot confirm. Playing with 13w18c on a world created with 1.1