Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.2.5) to the current pre-release (or weekly release).

New packets

Tab-complete (0xCB)

Two-way

Sent C->S when the user presses [tab] while writing text. The payload contains all text behind the cursor.

The server responds with an auto-completion of the last word sent to it. In the case of regular chat, this is a player username. Command names and parameters are also supported.

In the event of more than one possible completion, the server responds with the options packed into the single string field, separated by a null character. Note that as strings are UTF-16, this is two bytes wide.

Packet ID	Field Name	Field Type	Example	Notes
0xCB	Text	string
Total Size:	3 bytes + length of string

Locale and View Distance (0xCC)

Client to server

Sent when the player connects, or when settings are changed.

Packet ID	Field Name	Field Type	Example	Notes
0xCC	Locale	string	en_GB
	View distance	int	0	0-3 for 'far', 'normal', 'short', 'tiny'.
Total Size:	7 bytes + length of string

Changed packets

Hanshake (0x02)

Packet ID	Field Name	Field Type	Example	Notes
0x02	Protocol Version	byte	31
0x02	Username and Host	string	TkTech	The username of the player attempting to connect, and the host he is connecting to, seperated by a semicolon.
Total Size:	4 bytes + length of string

Protocol History

2012-04-26

• 12w17a
• Protocol version is now 31
• Changed packet: 0x02 Handshake
• ...

2012-04-19

• 12w16a
• Protocol version is now 30
• New packet: 0xCB Tab-complete
• New packet: 0xCC Locale and View Distance