Hi, my problem is when I call my method

public static void setFlightState(FlightState state) {
    	EntityPlayer p = Minecraft.getMinecraft().player;
    	if (getStateForPlayer(p) != state) {
	    	WingsPacketHandler.INSTANCE.sendToServer(new PacketFlightStateChange(state));
	    	if (state == FlightState.GLIDING) {
	    		p.capabilities.isFlying = false;
	    		try {
					setFlagMethod.invoke(Minecraft.getMinecraft().player, 7, true);
				} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
					e.printStackTrace();
					FMLCommonHandler.instance().exitJava(1, false);
				}
	    		
	    	} else {
	    		try {
					setFlagMethod.invoke(Minecraft.getMinecraft().player, 7, false);
				} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
					e.printStackTrace();
					FMLCommonHandler.instance().exitJava(1, false);
				}
	    		if (state == FlightState.HOVERING) {
	    			p.capabilities.isFlying = true;
	    		} else {
	    			p.capabilities.isFlying = false;
	    		}
	    	}
	    	tsc = 5;
    	}
    }

it should sent a packet to the server

import io.netty.buffer.ByteBuf;
import mods.giantnuker.wings.FlightState;
import mods.giantnuker.wings.ItemDetatchableWings;
import mods.giantnuker.wings.WingsCapability;
import mods.giantnuker.wings.WingsMod;
import net.minecraft.client.Minecraft;
import net.minecraft.entity.player.EntityPlayerMP;
import net.minecraft.inventory.EntityEquipmentSlot;
import net.minecraftforge.fml.common.FMLCommonHandler;
import net.minecraftforge.fml.common.network.simpleimpl.IMessage;
import net.minecraftforge.fml.common.network.simpleimpl.IMessageHandler;
import net.minecraftforge.fml.common.network.simpleimpl.MessageContext;

public class PacketFlightStateChange implements IMessage {
	FlightState s = FlightState.NOT_FLYING;
	public PacketFlightStateChange() {}
	public PacketFlightStateChange(FlightState f) {
		s = f;
	}

	@Override
	public void fromBytes(ByteBuf arg0) {
		s = FlightState.fromInt(arg0.readInt());
	}

	@Override
	public void toBytes(ByteBuf arg0) {
		arg0.writeInt(s.toInt());
	}
	public static class Handler implements IMessageHandler<PacketFlightStateChange, IMessage> {

		@Override
		public IMessage onMessage(PacketFlightStateChange arg0, MessageContext arg1) {
			EntityPlayerMP player = arg1.getServerHandler().player;
			WingsCapability cap = player.getCapability(WingsCapability.Provider.WINGS_CAP, null);
			//if (cap.hasWings() || player.getItemStackFromSlot(EntityEquipmentSlot.CHEST).getItem() == WingsMod.wings && ItemDetatchableWings.isUsable(player.getItemStackFromSlot(EntityEquipmentSlot.CHEST))) {
				FlightState state = arg0.s;
				if (state.equals(FlightState.GLIDING)) {
		    		player.capabilities.isFlying = false;
		    		try {
						WingsMod.setFlagMethod.invoke(Minecraft.getMinecraft().player, 7, true);
					} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
						e.printStackTrace();
						FMLCommonHandler.instance().exitJava(1, false);
					}
		    		
		    	} else {
		    		try {
		    			WingsMod.setFlagMethod.invoke(Minecraft.getMinecraft().player, 7, false);
					} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
						e.printStackTrace();
						FMLCommonHandler.instance().exitJava(1, false);
					}
		    		if (state.equals(FlightState.HOVERING)) {
		    			player.capabilities.isFlying = true;
		    		} else {
		    			player.capabilities.isFlying = false;
		    		}
		    	}
				System.out.println(state);
			//}
			return null;
		}
	}
}

the change happens on the client but not the server. It does NOT print the flight state & when I log out and back in again - I am falling out of the sky.

My Eyes Broke...

INSTANCE.registerMessage(PacketFlightStateChange.Handler.class, PacketFlightStateChange.class, 0, Side.CLIENT);

should be

INSTANCE.registerMessage(PacketFlightStateChange.Handler.class, PacketFlightStateChange.class, 0, Side.SERVER);