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).
Contents
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 | |
| Chat info | byte | Bits: 0: chat enabled, 2: colors enabled | ||
| View distance | int | 0 | 0-3 for 'far', 'normal', 'short', 'tiny'. | |
| Total Size: | 7 bytes + length of string | |||
Encryption Key Response (0xFC)
Client to server
Sent after receiving 0xFD.
| Packet ID | Field Name | Field Type | Example | Notes |
|---|---|---|---|---|
| 0xFC | Shared key length | short | ||
| Shared key | byte array | |||
| Total Size: | 3 bytes + length of key | |||
Encryption Key Request (0xFD)
Server to client
Sent after handshakes.
| Packet ID | Field Name | Field Type | Example | Notes |
|---|---|---|---|---|
| 0xFD | Server id | string | ||
| Public key length | short | |||
| Public key | byte array | |||
| Total Size: | 5 bytes + length of string + length of key | |||
Changed packets
Login Request (0x01)
Two-Way
Just a guess: stripped unused string field.
Client to Server
| Packet ID | Field Name | Field Type | Example | Notes |
|---|---|---|---|---|
| 0x01 | Protocol Version | int | 20
|
1.2.5's protocol version is 29
|
| Username | string | TkTech
|
The name of the user attempting to login, max length of 16 | |
| Not used | int | 0
|
||
| Not used | int | 0
|
||
| Not used | byte | 0
|
||
| Not used | unsigned byte | 0
|
||
| Not used | unsigned byte | 0
|
||
| Total Size: | 20 bytes + length of strings | |||
Server to Client
| Packet ID | Field Name | Field Type | Example | Notes |
|---|---|---|---|---|
| 0x01 | Entity ID | int | 1298
|
The Players Entity ID |
| Level Type | string | default | default or SUPERFLAT; level-type in server.properties | |
| Server mode | int | 0
|
0 for survival, 1 for creative | |
| Dimension | int | 0
|
-1: The Nether, 0: The Overworld, 1: The End
| |
| Difficulty | byte | 1
|
0 thru 3 for Peaceful, Easy, Normal, Hard
| |
| Not used | unsigned byte | 0
|
Only 0 observed from vanilla server, was previously world height | |
| Max players | unsigned byte | 8
|
Used by the client to draw the player list | |
| Total Size: | 20 bytes + length of strings | |||
Hanshake (0x02)
Client to server only
| Packet ID | Field Name | Field Type | Example | Notes |
|---|---|---|---|---|
| 0x02 | Protocol Version | byte | 31
|
|
| Username |
string | TkTech
|
The username of the player attempting to connect | |
| Total Size: | 4 bytes + length of string | |||
Protocol History
2012-04-26
- 12w17a
- Protocol version is now 31
- After exchanging handshakes, RC4 based encryption is initiated. The server sends 0xFD, which is replied by the client using 0xFC.
- Changed packet: 0x01 Login Request
- Changed packet: 0x02 Handshake
- Changed packet: 0xCC Locale and View Distance
- New packet: 0xFC Encryption Key Response
- New packet: 0xFD Encryption Key Request
2012-04-19
- 12w16a
- Protocol version is now 30
- New packet: 0xCB Tab-complete
- New packet: 0xCC Locale and View Distance
