Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.4.6, protocol 51) to the current pre-release (or weekly release). Note that this page contains bleeding-edge information that may not be completely or correctly documented.

New Packets

-None-

Changed Packets

Open Window (0x64)

Server to Client

This is sent to the client when it should open an inventory, such as a chest, workbench, or furnace. This message is not sent anywhere for clients opening their own inventory.

Packet ID	Field Name	Field Type	Example	Notes
0x64	Window id	byte	123	A unique id number for the window to be displayed. Notchian server implementation is a counter, starting at 1.
	Inventory Type	byte	2	The window type to use for display. Check below
	Window title	string	Chest	The title of the window.
	Number of Slots	byte	3	Number of slots in the window (excluding the number of slots in the player inventory).
	Use provided window title	boolean	1	If false, the client will look up a string like "window.minecart". If true, the client uses what the server provides.
Total Size:	6 bytes + length of string

Changed Data Types

Entity Metadata

Mobs

Index 5, string: Mob Name

The name to be displayed on the nameplate above the entity (If Show nameplate = 1).

Index 6, byte: Show nameplate

Set to 1 to show the nameplate, otherwise it is not displayed.

Minecart

Index 20, int: Block id & metadata

The id and metadata of the block to be shown in the minecart (If Show block = 1).

The block id can be obtained by: value & 0xFFFF.

The block metadata can be obtained by: value >> 16.

Index 21, int: Block position

The position (Y axis) of the block in the minecart. (Default: 6)

Index 22, byte: Show block

Set to 1 to show the block in the minecart, otherwise the block is not displayed.

Removed Packets

-None-

Protocol History

13w03a: Protocol version is now 53.

13w02a: All Minecart entities use object type 10, and send the block within seperately. Minecarts now send their type as object data in 0x17. Added boolean to 0x64 (Open Window) to determine whether or not to use the provided window title.