ClientCurrentPackMessage.java

package gr8pefish.ironbackpacks.network.client;

import gr8pefish.ironbackpacks.IronBackpacks;
import gr8pefish.ironbackpacks.capabilities.player.PlayerWearingBackpackCapabilities;
import io.netty.buffer.ByteBuf;
import net.minecraft.client.Minecraft;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.item.ItemStack;
import net.minecraftforge.fml.common.network.ByteBufUtils;
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 ClientCurrentPackMessage implements IMessage {

    //the data sent
    private ItemStack stack;

    public ClientCurrentPackMessage() {} //default constructor is necessary

    public ClientCurrentPackMessage(ItemStack stack) {
        this.stack = stack;
    }

    @Override
    public void fromBytes(ByteBuf buf){
        stack = ByteBufUtils.readItemStack(buf);
    }

    @Override
    public void toBytes(ByteBuf buf){
        ByteBufUtils.writeItemStack(buf, stack);
    }

    public static class Handler implements IMessageHandler<ClientCurrentPackMessage, IMessage> {

        @Override
        public IMessage onMessage(ClientCurrentPackMessage message, MessageContext ctx) {

            //have to use threading system since 1.8
            Minecraft.getMinecraft().addScheduledTask(() -> {
                EntityPlayer player = IronBackpacks.proxy.getClientPlayer();
                if (player != null) {
                    PlayerWearingBackpackCapabilities.setCurrentBackpack(player, message.stack); //update the backpack
                }
            });

            return null; //no return message
        }
    }
}