Xjyuk

I use MInecraftEdu in my geography classes. The servers work fine in three classes and fail repeatedly in the fourth. The failures occur soon after starting new worlds. I have noticed some students putting odd characters into chat. Central office confirms that nothing different is going on in the network during the class period. Below is one crash log, with names redacted:

---- Minecraft Crash Report ----
// You should try our sister game, Minceraft!

Time: 1/22/15 2:31 PM
Description: Loading NBT data

java.util.zip.ZipException: incorrect data check
 at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:147)
 at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
 at java.io.BufferedInputStream.read1(BufferedInputStream.java:258)
 at java.io.BufferedInputStream.read(BufferedInputStream.java:317)
 at java.io.DataInputStream.readFully(DataInputStream.java:178)
 at java.io.DataInputStream.readFully(DataInputStream.java:152)
 at net.minecraft.nbt.NBTTagByteArray.func_152446_a(SourceFile:28)
 at net.minecraft.nbt.NBTTagCompound.func_152449_a(SourceFile:329)
 at net.minecraft.nbt.NBTTagCompound.func_152446_a(SourceFile:41)
 at net.minecraft.nbt.NBTTagList.func_152446_a(NBTTagList.java:52)
 at net.minecraft.nbt.NBTTagCompound.func_152449_a(SourceFile:329)
 at net.minecraft.nbt.NBTTagCompound.func_152446_a(SourceFile:41)
 at net.minecraft.nbt.NBTTagCompound.func_152449_a(SourceFile:329)
 at net.minecraft.nbt.NBTTagCompound.func_152446_a(SourceFile:41)
 at net.minecraft.nbt.CompressedStreamTools.func_152455_a(CompressedStreamTools.java:168)
 at net.minecraft.nbt.CompressedStreamTools.func_152456_a(CompressedStreamTools.java:125)
 at net.minecraft.nbt.CompressedStreamTools.func_74794_a(CompressedStreamTools.java:120)
 at net.minecraft.world.chunk.storage.AnvilChunkLoader.loadChunk__Async(AnvilChunkLoader.java:121)
 at net.minecraftforge.common.chunkio.ChunkIOProvider.callStage1(ChunkIOProvider.java:20)
 at net.minecraftforge.common.chunkio.ChunkIOProvider.callStage1(ChunkIOProvider.java:12)
 at net.minecraftforge.common.util.AsynchronousExecutor.skipQueue(AsynchronousExecutor.java:343)
 at net.minecraftforge.common.util.AsynchronousExecutor.getSkipQueue(AsynchronousExecutor.java:302)
 at net.minecraftforge.common.chunkio.ChunkIOExecutor.syncChunkLoad(ChunkIOExecutor.java:12)
 at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:126)
 at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:101)
 at net.minecraft.world.gen.ChunkProviderServer.func_73154_d(ChunkProviderServer.java:199)
 at net.minecraft.world.World.func_72964_e(World.java:435)
 at net.minecraft.world.WorldServer.func_147456_g(WorldServer.java:320)
 at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:190)
 at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:693)
 at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:357)
 at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:615)
 at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:494)
 at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:754)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
 at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:147)
 at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
 at java.io.BufferedInputStream.read1(BufferedInputStream.java:258)
 at java.io.BufferedInputStream.read(BufferedInputStream.java:317)
 at java.io.DataInputStream.readFully(DataInputStream.java:178)
 at java.io.DataInputStream.readFully(DataInputStream.java:152)
 at net.minecraft.nbt.NBTTagByteArray.func_152446_a(SourceFile:28)

-- NBT Tag --
Details:
 Tag name: BlockLight
 Tag type: 7
Stacktrace:
 at net.minecraft.nbt.NBTTagCompound.func_152449_a(SourceFile:329)
 at net.minecraft.nbt.NBTTagCompound.func_152446_a(SourceFile:41)
 at net.minecraft.nbt.NBTTagList.func_152446_a(NBTTagList.java:52)
 at net.minecraft.nbt.NBTTagCompound.func_152449_a(SourceFile:329)
 at net.minecraft.nbt.NBTTagCompound.func_152446_a(SourceFile:41)
 at net.minecraft.nbt.NBTTagCompound.func_152449_a(SourceFile:329)
 at net.minecraft.nbt.NBTTagCompound.func_152446_a(SourceFile:41)
 at net.minecraft.nbt.CompressedStreamTools.func_152455_a(CompressedStreamTools.java:168)
 at net.minecraft.nbt.CompressedStreamTools.func_152456_a(CompressedStreamTools.java:125)
 at net.minecraft.nbt.CompressedStreamTools.func_74794_a(CompressedStreamTools.java:120)
 at net.minecraft.world.chunk.storage.AnvilChunkLoader.loadChunk__Async(AnvilChunkLoader.java:121)
 at net.minecraftforge.common.chunkio.ChunkIOProvider.callStage1(ChunkIOProvider.java:20)
 at net.minecraftforge.common.chunkio.ChunkIOProvider.callStage1(ChunkIOProvider.java:12)
 at net.minecraftforge.common.util.AsynchronousExecutor.skipQueue(AsynchronousExecutor.java:343)
 at net.minecraftforge.common.util.AsynchronousExecutor.getSkipQueue(AsynchronousExecutor.java:302)
 at net.minecraftforge.common.chunkio.ChunkIOExecutor.syncChunkLoad(ChunkIOExecutor.java:12)
 at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:126)
 at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:101)
 at net.minecraft.world.gen.ChunkProviderServer.func_73154_d(ChunkProviderServer.java:199)
 at net.minecraft.world.World.func_72964_e(World.java:435)
 at net.minecraft.world.WorldServer.func_147456_g(WorldServer.java:320)
 at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:190)

-- Affected level --
Details:
 Level name: ../worlds/tmpworld
 All players: 10 total; [EntityPlayerMP[‘A’/0, l='../worlds/tmpworld', x=199.95, y=97.49, z=40.08], EntityPlayerMP[‘B’/1, l='../worlds/tmpworld', x=-305.14, y=90.56, z=-580.19], EntityPlayerMP[‘C’/2, l='../worlds/tmpworld', x=290.85, y=65.00, z=-223.48], EntityPlayerMP[‘D’/3, l='../worlds/tmpworld', x=290.64, y=66.00, z=-227.27], EntityPlayerMP[‘E’/4, l='../worlds/tmpworld', x=-542.45, y=67.87, z=550.04], EntityPlayerMP[‘F’/5, l='../worlds/tmpworld', x=-599.12, y=101.38, z=231.63], EntityPlayerMP[‘G’/8, l='../worlds/tmpworld', x=-186.06, y=72.35, z=-3.29], EntityPlayerMP[‘H’/9, l='../worlds/tmpworld', x=-21.50, y=85.90, z=-193.03], EntityPlayerMP[‘I’/11, l='../worlds/tmpworld', x=6.52, y=70.11, z=-14.52], EntityPlayerMP[‘J’/23, l='../worlds/tmpworld', x=-8.50, y=67.97, z=5.50]]
 Chunk stats: ServerChunkCache: 2956 Drop: 0
 Level seed: 6921963374414891008
 Level generator: ID 00 - default, ver 1. Features enabled: true
 Level generator options: 
 Level spawn location: World: (0,65,0), Chunk: (at 0,4,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
 Level time: 60509 game time, 60509 day time
 Level dimension: 0
 Level storage version: 0x04ABD - Anvil
 Level weather: Rain time: 76000 (now: false), thunder time: 155577 (now: false)
 Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
 at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:693)
 at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:357)
 at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:615)
 at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:494)
 at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:754)

-- System Details --
Details:
 Minecraft Version: 1.7.10
 Operating System: Mac OS X (x86_64) version 10.10.1
 Java Version: 1.6.0_65, Apple Inc.
 Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
 Memory: 214971832 bytes (205 MB) / 503984128 bytes (480 MB) up to 4286251008 bytes (4087 MB)
 JVM Flags: 1 total; -Xmx4096M
 AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
 IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
 FML: MCP v9.03 FML v7.10.25.0 Minecraft Forge 10.13.0.1208 4 mods loaded, 4 mods active
 mcp9.05 [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
 FML7.10.25.0 [Forge Mod Loader] (minecraftedu_server.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
 Forge10.13.0.1208 [Minecraft Forge] (minecraftedu_server.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
 mcedu1.7.10 [MinecraftEdu] (minecraftedu_server.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
 Profiler Position: N/A (disabled)
 Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
 Player Count: 10 / 100; [EntityPlayerMP['AMYIAH'/0, l='../worlds/tmpworld', x=199.95, y=97.49, z=40.08], EntityPlayerMP['aaa'/1, l='../worlds/tmpworld', x=-305.14, y=90.56, z=-580.19], EntityPlayerMP[‘bob’/2, l='../worlds/tmpworld', x=290.85, y=65.00, z=-223.48], EntityPlayerMP[‘ccc’/3, l='../worlds/tmpworld', x=290.64, y=66.00, z=-227.27], EntityPlayerMP[‘ddd’/4, l='../worlds/tmpworld', x=-542.45, y=67.87, z=550.04], EntityPlayerMP[‘fff’/5, l='../worlds/tmpworld', x=-599.12, y=101.38, z=231.63], EntityPlayerMP[‘ggg’/8, l='../worlds/tmpworld', x=-186.06, y=72.35, z=-3.29], EntityPlayerMP[‘C’/9, l='../worlds/tmpworld', x=-21.50, y=85.90, z=-193.03], EntityPlayerMP[‘K’/11, l='../worlds/tmpworld', x=6.52, y=70.11, z=-14.52], EntityPlayerMP[‘G’/23, l='../worlds/tmpworld', x=-8.50, y=67.97, z=5.50]]
 Is Modded: Definitely; Server brand changed to 'fml,forge'
 Type: Dedicated Server (map_server.txt)

This is from a incorrect data check coming from java's zip file support (minecraft worlds are compressed)

When data is saved in this manner, a small checksum is included to verify the integrity of the data, this error arises when the stored checksum does not match the checksum of the newly-extracted data.

This is likely due to a failing hard disk, or the server software being exited without being properly stopped. (the stop command, either at the console, or as a logged-in op is the correct way to stop the server). Other possible causes are the failure of a hard disk, or a bad download-copy of the world.

It is highly unlikely that any of your students could have caused this error to arise.

Because you are using modded minecraft (MinecraftEDU is a mod), you cannot use the Minecraft Region Fixer... So your best bet is to delete the affected region file, you will loose all of the changes made to the land contained in said file. Unfortunately, the log does not contain the name of the affected region file, so you will simply have to back up the world, and delete half of the files (they are of type *.mca, and stored in worldfolder/region) and repeat until you are able to determine which specific file is causing the issue. Then remove it... An area of 8192 m^2 will be reset to its original generation.

It is possible that a more precise recover could be performed, but that would require custom software.

~Edit. It seems that Region Fixer does support modded worlds. See https://github.com/Fenixin/Minecraft-Region-Fixer/blob/master/README.rst for instructions and downloads.

I see that you are on OSX, I don't know if python (which this needs to run) is preinstalled or not. However your IT department should be able to help you with that.