Syncing Tile Entities in Minecraft Forge 1.15

SyncingTileEntitiesInMinecraftForgeOnePointFifteen.java

/** TLDR
 * Update Tag -> sent when client loads the chunk the TE is in
 * Update Packet -> sent when you call world.notifyBlockUpdate
 **/


public class YourTileEntity extends TileEntity
{

  public YourTileEntity()
	{
		this(yourTileEntityType);
	}
  
  // some data we'll be saving and syncing
  public int data;
  
  // we can tell the server to save the TileEntity's state to the hard drive by
  // calling someTileEntity.markDirty()
  
  // called to load the TE onto the server from the hard drive
	@Override
	public void read(CompoundNBT compound)
	{
		super.read(compound);
		this.data = compound.getInt("data");
	}

  // called to save the TE to the hard drive from the server
	@Override
	public CompoundNBT write(CompoundNBT compound)
	{
		CompoundNBT nbt = super.write(compound);
		nbt.putInt(this.data);
    return nbt;
	}
	
  // called to generate NBT for a syncing packet when a client loads a chunk that this TE is in
	@Override
	public CompoundNBT getUpdateTag()
	{
    // we want to tell the client about as much data as it needs to know
    // since it doesn't know any data at this point, we can usually just defer to write() above
      // if you have data that would be written to the disk but the client doesn't ever need to know,
      // you can just sync the need-to-know data instead of calling write()
    // there's an equivalent method for reading the update tag but it just defaults to read() anyway
		return this.write(new CompoundNBT());
	}
	
  // we can sync a TileEntity from the server to all tracking clients by calling world.notifyBlockUpdate
  
  // when that happens, this method is called on the server to generate a packet to send to the client
  // if you have lots of data, it's a good idea to keep track of which data has changed since the last time
  // this TE was synced, and then only send the changed data;
  // this reduces the amount of packets sent, which is good
  // we only have one value to sync so we'll just write everything into the NBT again
	@Override
	public SUpdateTileEntityPacket getUpdatePacket()
	{
		CompoundNBT nbt = new CompoundNBT();
		this.write(nbt);
		
		// the number here is generally ignored for non-vanilla TileEntities, 0 is safest
		return new SUpdateTileEntityPacket(this.getPos(), 0, nbt);
	}
	
  // this method gets called on the client when it receives the packet that was sent in the previous method
	@Override
	public void onDataPacket(NetworkManager net, SUpdateTileEntityPacket packet)
	{
		this.read(packet.getNbtCompound());
	}
}