I use a forge server on my local lan to play with my kids. With the latest dev version I get the following crash:

Description: Exception in server tick loop

net.minecraftforge.fml.common.LoaderException: java.lang.NoClassDefFoundError: com/mrcrayfish/furniture/entity/EntityMirror
at net.minecraftforge.fml.common.LoadController.transition(LoadController.java:162)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:693)
at net.minecraftforge.fml.server.FMLServerHandler.finishServerLoading(FMLServerHandler.java:97)
at net.minecraftforge.fml.common.FMLCommonHandler.onServerStarted(FMLCommonHandler.java:360)
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:210)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:438)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NoClassDefFoundError: com/mrcrayfish/furniture/entity/EntityMirror
at com.mrcrayfish.furniture.MrCrayfishFurnitureMod.init(MrCrayfishFurnitureMod.java:131)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:518)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:208)
at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:187)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:118)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:692)
... 5 more
Caused by: java.lang.ClassNotFoundException: com.mrcrayfish.furniture.entity.EntityMirror
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 33 more
Caused by: net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerException: Exception in class transformer net.minecraftforge.fml.common.asm.transformers.SideTransformer@20435c40 from coremod FMLCorePlugin
at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:234)
at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176)
... 35 more
Caused by: java.lang.RuntimeException: Attempted to load class com/mrcrayfish/furniture/entity/EntityMirror for invalid side SERVER
at net.minecraftforge.fml.common.asm.transformers.SideTransformer.transform(SideTransformer.java:49)
at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:230)
... 37 more

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

-- System Details --
Details:
Minecraft Version: 1.8
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_60, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 789141392 bytes (752 MB) / 925892608 bytes (883 MB) up to 3797417984 bytes (3621 MB)
JVM Flags: 0 total;
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v9.10 FML v8.0.37.1334 Minecraft Forge 11.14.1.1334 4 mods loaded, 4 mods active
mcp{9.05} Minecraft Coder Pack Unloaded->Constructed->Pre-initialized->Initialized
FML{8.0.37.1334} Forge Mod Loader Unloaded->Constructed->Pre-initialized->Initialized
Forge{11.14.1.1334} Minecraft Forge Unloaded->Constructed->Pre-initialized->Initialized
cfm{3.5} §9MrCrayfish's Furniture Mod Unloaded->Constructed->Pre-initialized->Errored
Loaded coremods (and transformers):
Profiler Position: N/A (disabled)
Is Modded: Definitely; Server brand changed to 'fml,forge'
Type: Dedicated Server (map_server.txt)

Latest commits resolve this.

Hellow !

Still have that error with v3.5-dev version.

---- Minecraft Crash Report ----
// Ouch. That hurt :(

Time: 03/11/15 20:16
Description: Exception in server tick loop

net.minecraftforge.fml.common.LoaderException: java.lang.NoClassDefFoundError: com/mrcrayfish/furniture/entity/EntityMirror
at net.minecraftforge.fml.common.LoadController.transition(LoadController.java:163)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:733)
at net.minecraftforge.fml.server.FMLServerHandler.finishServerLoading(FMLServerHandler.java:97)
at net.minecraftforge.fml.common.FMLCommonHandler.onServerStarted(FMLCommonHandler.java:360)
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:210)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:438)
at java.lang.Thread.run(Thread.java:701)
Caused by: java.lang.NoClassDefFoundError: com/mrcrayfish/furniture/entity/EntityMirror
at com.mrcrayfish.furniture.MrCrayfishFurnitureMod.init(MrCrayfishFurnitureMod.java:131)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:622)
at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:537)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:622)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:212)
at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:190)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:622)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:119)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:731)
... 5 more
Caused by: java.lang.ClassNotFoundException: com.mrcrayfish.furniture.entity.EntityMirror
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
... 33 more
Caused by: net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerException: Exception in class transformer net.minecraftforge.fml.common.asm.transformers.SideTransformer@59e0b2fa from coremod FMLCorePlugin
at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:234)
at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176)
... 35 more
Caused by: java.lang.RuntimeException: Attempted to load class com/mrcrayfish/furniture/entity/EntityMirror for invalid side SERVER
at net.minecraftforge.fml.common.asm.transformers.SideTransformer.transform(SideTransformer.java:49)
at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:230)
... 37 more

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

-- System Details --
Details:
Minecraft Version: 1.8
Operating System: Linux (amd64) version 3.2.0-4-amd64
Java Version: 1.6.0_36, Sun Microsystems Inc.
Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Sun Microsystems Inc.
Memory: 1351088096 bytes (1288 MB) / 1544814592 bytes (1473 MB) up to 1544814592 bytes (1473 MB)
JVM Flags: 2 total; -Xmx1524M -Xms1524M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v9.10 FML v8.0.99.99 Minecraft Forge 11.14.3.1543 4 mods loaded, 4 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCHI mcp{9.05} Minecraft Coder Pack
UCHI FML{8.0.99.99} Forge Mod Loader
UCHI Forge{11.14.3.1543} Minecraft Forge
UCHE cfm{3.5} �9MrCrayfish's Furniture Mod
Loaded coremods (and transformers):
Profiler Position: N/A (disabled)
Is Modded: Definitely; Server brand changed to 'fml,forge'
Type: Dedicated Server (map_server.txt)