Pocket Minecraft Protocol

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Unlike the Minecraft protocol, this protocol uses UDP with (so far observed, at least) one message per packet. This makes the protocol easier to work with when it comes to packet serialization, and might offer latency improvements, but will inevitably have the usual UDP issues (packets lost, truncated, duplicated, out-of-order, etc.).

Servers listen on UDP port 19132.

Clients don't pick any specific port to listen on.


Please note that even where packet field names are written in this page, these are still largely hypothetical and could well be incorrect guesses. Some packets are fixed to the RakNet protocol, and will be marked as "RakNet Packet", which means that these packets will not change on future versions.

It has been determined that PM uses RakNet for its networking library, some documentation that seems relevant.


Terminology

PM
Pocket Minecraft (aka Minecraft PE or Minecraft Pocket Edition)

Types

Size Range Notes
byte 1 -128 to 127 Signed, two's complement
short 2 -32768 to 32767 Signed, two's complement
int32 4 -2147483648 to 2147483647 Signed, two's complement
int64 8 Maybe a double?
MAGIC 16 0x00ffff00fefefefefdfdfdfd12345678 always hex bytes 0x00ffff00fefefefefdfdfdfd12345678, corresponding to RakNet's default OFFLINE_MESSAGE_DATA_ID
string ≥ 1 N/A Prefixed by a short containing the length of the string in characters. It appears that only the following ASCII characters can be displayed: !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~

Packets

All packets start with a single byte that identifies the packet type, the rest of the packet follows it.


ID_UNCONNECTED_PING_OPEN_CONNECTIONS (0x02)

Client to Broadcast


RakNet Packet

Packet ID Field Name Field Type Example Notes
0x02 Ping ID int64 0x00000000003c6d0d Time since start in Milliseconds
MAGIC MAGIC
Total Size: 25 Bytes

Clients start out by sending this packet to the IP broadcast address on port 19132 repeatedly (approx once per second) when joining a server was chosen on the main screen, and stops when the user selects a server (or leaves the screen). The ping ID from the client increases over time, and appears to be the number of milliseconds since the client program was started (might be used to measure server response latency).


ID_OPEN_CONNECTION_REQUEST_1 (0x05)

Client to Server


RakNet Packet

Packet ID Field Name Field Type Example Notes
0x05 MAGIC MAGIC
Protocol Version byte 5 Currently 5
Null Payload many 0x00 bytes 0x00 * 1447 MTU (Maximum Transport Unit)
Total Size: 18 Bytes + lenght of Null Payload

If the version is different than yours, reply with a ID_INCOMPATIBLE_PROTOCOL_VERSION (0x1A)

Sent from client after it receives packet 0x1d. The client will repeatedly send this with reducing sizes until it successfully receives a reply. Observed behaviour is that the client will send packets ~0.5s apart in the following way, until it gets a 0x06 response packet, or reaches the end of these:

  • 4 packets of Null Payload lenght of 1447
  • 4 packets of Null Payload lenght of 1155
  • 5 packets of Null Payload lenght of 531

If the server doesnt't reply the client, the client will display a "Connect Error" window


ID_OPEN_CONNECTION_REPLY_1 (0x06)

Server to Client


RakNet Packet

Packet ID Field Name Field Type Example Notes
0x06 MAGIC MAGIC
Server ID int64 0x00000000372cdc9e This value seems to be constant for an installation of PM, or differs between the demo and full version.
Server Security byte 0 Always 0
MTU Size short 1447 Lenght of 0x05. Used to determine packet loss and max UDP packet size (MTU)
Total Size: 28 Bytes

Sent from server after it receives packet 0x05.


ID_OPEN_CONNECTION_REQUEST_2 (0x07)

Client to Server


RakNet Packet

Packet ID Field Name Field Type Example Notes
0x07 MAGIC MAGIC
Security + Cookie 1 + 4 bytes 0x043f57fefd Unused, constant value
Server UDP Port short 19132
MTU Size short 1464
Client ID int64 0x00000000372cdc9e The Client / Server ID will be the same for a given device
Total Size: 34 Bytes

Sent from client in response to packet 0x06.


ID_OPEN_CONNECTION_REPLY_2 (0x08)

Server to Client


RakNet Packet

Packet ID Field Name Field Type Example Notes
0x08 MAGIC MAGIC
Server ID int64 0x00000000372cdc9e
Client UDP Port short 46946
MTU Size short 1464
Security byte 0 Always 0
Total Size: 30 Bytes

Sent from server in response to packet 0x07.


ID_INCOMPATIBLE_PROTOCOL_VERSION (0x1A)

Server to Client


RakNet Packet

Packet ID Field Name Field Type Example Notes
0x1A Protocol Version byte 5
MAGIC MAGIC
Server ID int64 0x00000000372cdc9e
Total Size: 26 Bytes


ID_UNCONNECTED_PING_OPEN_CONNECTIONS (0x1C)

Server to Client


RakNet Packet

Packet ID Field Name Field Type Example Notes
0x1C Ping ID int64 0x00000000003c6d0d Time since start in Milliseconds
Server ID int64 0x00000000372cdc9e
MAGIC MAGIC
Data string MCCPP;Demo;Steve Used to send the username (MCCPP;Demo; + username)
Total Size: 35 Bytes + lenght of string

Server sends this packet in response to a 0x02 packet. Depends of the version to send a 0x1D or a 0x1C If the Server is invisible, this packet will be sent without username


ID_ADVERTISE_SYSTEM (0x1D)

Server to Client


RakNet Packet

Packet ID Field Name Field Type Example Notes
0x1D Ping ID int64 0x00000000003c6d0d Time since start in Milliseconds
Server ID int64 0x00000000372cdc9e
MAGIC MAGIC
Data string MCCPP;Demo;Steve Used to send the username (MCCPP;Demo; + username)
Total Size: 35 Bytes + lenght of string

Same as ID_UNCONNECTED_PING_OPEN_CONNECTIONS (0x1C), but with the Packet ID changed. Depends of the version to send a 0x1D or a 0x1C


ID_RESERVED_7 (0x84)

Two-Way

This packet is part of the real Minecraft PE implementation. The structure can change anytime.


This packet has a partial unknown structure

Packet ID Field Name Field Type Example Notes
0x84 Packet Order ID byte? 2 Could be used to reorder packets
? Integer? 00 00 40 00 These 4 bytes seem to always be the same. Needs confirmation.
Unknown variable
Total Size: 1 + ? Bytes

Sent after 0x08, and 0xC0. Packet Order is independient from server/client

Different 0x84 values sent in a session, use this to help understand this packet


Unknown (0x8C)

Server -> Client

This packet is part of the real Minecraft PE implementation. The structure can change anytime.


This packet has a partial unknown structure, but it seems to complement the packet 0x84. Packet Order count continues from the last value of 0x84. Could be Chunk Data or AddEntityPacket.

It seems that it has a start field of unknown lenght that suggests that this packet is used as an multi-purpouse packet. The same happens with 0x84

Packet ID Field Name Field Type Example Notes
0x8C Packet Order ID byte? 57 Could be used to reorder packets
Unknown variable
Total Size: 1 + ? Bytes

Sent after 0x84 by client.


Unknown (0xA0)

Two-Way

This packet is part of the real Minecraft PE implementation. The structure can change anytime.

Packet ID Field Name Field Type Example Notes
0xA0 Data 6 bytes 0x000101000000
Total Size: 7 Bytes

Sent after an invalid Packet Order ID.


Unknown (0xC0)

Two-Way

This packet is part of the real Minecraft PE implementation. The structure can change anytime.

Packet ID Field Name Field Type Example Notes
0xC0 Data 6 bytes 0x000101000000 Maybe dependent of firsth 0x84
Total Size: 7 Bytes

Sent after the first 0x84. Then, the peer replies with the same packet. Could be used to ACK recieval of packets.


Packet Dumps

Due to the lack of information about the protocol, packet dumps are welcome. You can also post here pcap files of Client <-> Server sessions

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