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

13w02a: Added boolean to 0x64 (Open Window) to determine whether or not to use the provided window title.