java.lang.NoClassDefFoundError: net/minecraft/network/NetHandlerPlayServer
    at net.minecraftforge.fml.common.network.internal.FMLNetworkHandler.fmlServerHandshake(FMLNetworkHandler.java:71)
    at net.minecraft.server.network.NetHandlerLoginServer.func_147326_c(NetHandlerLoginServer.java:135)
    at net.minecraft.server.network.NetHandlerLoginServer.func_73660_a(NetHandlerLoginServer.java:63)
    at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:285)
    at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:179)
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:788)
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:666)
    at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:239)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:524)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: net.minecraft.network.NetHandlerPlayServer
    at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:101)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 10 more