_GrumpyBear

Thanks, it worked. I tried passing ctx.getServerHandler().entityPlayer.getActiveItemStack() for the ItemStack near the start but it didn't work, but calling getHeldItemMainhand() worked instead.

I'm trying to set up a mode changing system wherein when the user presses a key, the mode int tag of an ItemStack's NBT is incremented by 1. @SubscribeEvent public void keyDown(TickEvent.ClientTickEvent e) { if (e.phase == TickEvent.Phase.END) { Minecraft mc = Minecraft.getMinecraft(); if (mc.world != null) { ItemStack stack = mc.player.getHeldItemMainhand(); if (key.isPressed()) if (stack != null) { IModeItem item = (IModeItem) stack.getItem(); if (item instanceof ItemVoidVacuum) { if (item.getMode(stack) != 0) { int result = item.getMode(stack) == 1 ? 2 : 1; item.setModeClient(stack, result); ChromEngPacketHandler.INSTANCE.sendToServer(new MessageSetMode(stack, result)); } } } } } default void setModeClient(ItemStack stack, int i) { ItemStackUtil.getNBT(stack).setInteger("Mode", i); } public class MessageSetMode implements IMessage{ private ItemStack stack; private int modeNo; public MessageSetMode() { } public MessageSetMode(ItemStack stack, int modeNo) { this.stack = stack; this.modeNo = modeNo; } @Override public void fromBytes(ByteBuf buf) { this.stack = ByteBufUtils.readItemStack(buf); this.modeNo = buf.readInt(); } @Override public void toBytes(ByteBuf buf) { ByteBufUtils.writeItemStack(buf, this.stack); buf.writeInt(modeNo); } public static class MessageSetModeHandler implements IMessageHandler<MessageSetMode, IMessage> { @Override public IMessage onMessage(MessageSetMode message, MessageContext ctx) { ((IModeItem) message.stack.getItem()).setModeClient(message.stack, message.modeNo); return null; } } } However, when this conditional statement is called: if (getMode(player.getHeldItemMainhand()) == 0) { NBTUtil.writeBlockState(voidNBT, worldIn.getBlockState(pos)); worldIn.setBlockToAir(pos); setModeClient(player.getHeldItemMainhand(), prefMode); } else if (getMode(player.getHeldItemMainhand()) == 1) { worldIn.setBlockState(pos.offset(facing), NBTUtil.readBlockState(voidNBT)); worldIn.spawnParticle(EnumParticleTypes.END_ROD, pos.offset(facing).getX(), pos.offset(facing).getY(), pos.offset(facing).getZ(), 5, 5, 5); setModeClient(player.getHeldItemMainhand(), 0); prefMode = 1; } else if (getMode(player.getHeldItemMainhand()) == 2) { NBTUtil.writeBlockState(voidNBT, Blocks.AIR.getDefaultState()); setModeClient(player.getHeldItemMainhand(), 0); prefMode = 2; } default int getMode(ItemStack stack) { return ItemStackUtil.getNBT(stack).getInteger("Mode"); } On the client side, when the mode is equal to 2, the final else if is called, while on the server side, the first else if is called. I checked while debugging and when the mode is switched, the value on client and server side is 2, but when getMode is called in the Item class, the client's mode is 2 while the server's is 1. Sorry if the answer is painfully obvious, I've been trying the whole day and can't see the problem.