[19:53:17 INFO]: This server is running CraftBukkit version git-Bukkit-0cd0397 (MC: 1.9.4) (Implementing API version 1.9.4-R0.1-SNAPSHOT)
[19:53:17 ERROR]: Could not load 'plugins\BukkitPiano.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.NoClassDefFoundError: net/minecraft/server/v1_11_R1/Packet
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:133) ~[craftbukkit.jar:git-Bukkit-0cd0397]
        at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:328) ~[craftbukkit.jar:git-Bukkit-0cd0397]
        at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [craftbukkit.jar:git-Bukkit-0cd0397]
        at org.bukkit.craftbukkit.v1_9_R2.CraftServer.loadPlugins(CraftServer.java:294) [craftbukkit.jar:git-Bukkit-0cd0397]
        at org.bukkit.craftbukkit.v1_9_R2.CraftServer.<init>(CraftServer.java:256) [craftbukkit.jar:git-Bukkit-0cd0397]
        at net.minecraft.server.v1_9_R2.PlayerList.<init>(PlayerList.java:70) [craftbukkit.jar:git-Bukkit-0cd0397]
        at net.minecraft.server.v1_9_R2.DedicatedPlayerList.<init>(SourceFile:14) [craftbukkit.jar:git-Bukkit-0cd0397]
        at net.minecraft.server.v1_9_R2.DedicatedServer.init(DedicatedServer.java:181) [craftbukkit.jar:git-Bukkit-0cd0397]
        at net.minecraft.server.v1_9_R2.MinecraftServer.run(MinecraftServer.java:510) [craftbukkit.jar:git-Bukkit-0cd0397]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_121]
Caused by: java.lang.NoClassDefFoundError: net/minecraft/server/v1_11_R1/Packet
        at java.lang.Class.forName0(Native Method) ~[?:1.8.0_121]
        at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_121]
        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[craftbukkit.jar:git-Bukkit-0cd0397]
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129) ~[craftbukkit.jar:git-Bukkit-0cd0397]
        ... 9 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.v1_11_R1.Packet
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:67) ~[craftbukkit.jar:git-Bukkit-0cd0397]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[craftbukkit.jar:git-Bukkit-0cd0397]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_121]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_121]
        at java.lang.Class.forName0(Native Method) ~[?:1.8.0_121]
        at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_121]
        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[craftbukkit.jar:git-Bukkit-0cd0397]
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129) ~[craftbukkit.jar:git-Bukkit-0cd0397]
        ... 9 more