Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.8.1) to the current pre-release (currently 1.9pre4)

New packets

Enchant Item (0x6C)

Client to Server only

Packet ID	Field Name	Field Type	Example	Notes
0x6C	Window ID	byte	1	The ID sent by 0x64
	Enchantment	byte	0	The position of the enchantment on the enchantment table window, starting with 0 as the topmost one.
Total Size:	3 bytes

Changed packets

"Slot" type change

Four packets changed:

• 0x0F player block placement
• 0x66 window click
• 0x67 set slot
• 0x68 window items

This change affects the "slot" datatype. This type consists of at least a short (item_id). If this id isn't -1, a byte (count) and a short (uses) follow.

From 1.9pre2 onward, additional data is sent but only for certain item_ids. This means the protocol is no longer context free. The additional data is at least a short. If this short isn't -1, a byte[] array follows, containing gzipped NBT data

As of 1.9pre3, the format of the NBT is as follows

 COMPOUND
   LIST: 'ench'
     SHORT: 'id'
     SHORT: 'lvl'
   END
 END

Experience (0x2B)

Now float, short, short

Other changes

Protocol version is 20, as of 1.9pre4

New mobs: Blaze, Magma Cube, Ender Dragon, Snowman, Villager

Notchian server features two new protocols: RCON (server class: o.java) and G4S [1]

Protocol History

Provided below is a changelog of the server protocol starting on 2010-08-20. The wiki history feature may also be used to investigate changes.

2011-10-13

• Beta 1.9 pre4-release.
• Protocol version is now 20
• Packet 0x2B (Experience) changed: now (float, short, short)
• New packet 0x6C (Unknown) added: (byte, byte)
• Flint and steel no longer enchantable (see 1.9pre3 changes). Might be others, too.
• Notchian server now features an RCON server (server class: o.java)
• Notchian server now features "G4S" server [2]

2011-9-29

• Beta 1.9 pre2-release.
• Protocol version is now 19
• Four packets changed:
  • 0x0F player block placement
  • 0x66 window click
  • 0x67 set slot
  • 0x68 window items
• The change affects the "slot" datatype. This type consists of at least a short (item_id). If this id isn't -1, a byte (count) and a short (uses) follow.
• From 1.9pre2 onward, additional data is sent but only for certain item_ids. This means the protocol is no longer context free. The additional data is at least a short. If this short isn't -1, a byte[] array follows, containing gzipped NBT data
• The format of the NBT is as follows

 COMPOUND
   LIST: 'ench'
     SHORT: 'id'
     SHORT: 'lvl'
   END
 END

• So far only this format, with 'id' and 'lvl' set to 2 and 1 respectively, has been seen.

2011-9-22

• Beta 1.9 pre-release.
• Protocol version is now 18