Pocket Minecraft Protocol

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.).

Old servers listen on UDP port 19132. As of the survival update, the port is the same 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.

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

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

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

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 After this the client appears not to send any more packets to the server, but also doesn't (at least immediately) leave the "locating server" progress screen. 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

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.
	Unused	byte	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

Packet ID	Field Name	Field Type	Example	Notes
0x07	MAGIC	MAGIC
	Unused	5 bytes	0x043f57fefd	Only seen this value
	Port	short	19132
	MTU Size	short	1464
	Client ID	int64	0x00000000372cdc9e	The Client / Server ID will be the same for a device
	Total Size:	39 Bytes

Sent from client in response to packet 0x06.

ID_OPEN_CONNECTION_REPLY_2 (0x08)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x08	MAGIC	MAGIC
	Server ID	int64	0x00000000372cdc9e
	Unused	5 bytes	0x043f57fefd
	Total Size:	30 Bytes

Sent from server in response to packet 0x07.

ID_ADVERTISE_SYSTEM (0x1D)

Same as ID_UNCONNECTED_PING_OPEN_CONNECTIONS (0x1C), but with the Packet ID changed. Depends of the version

ID_UNCONNECTED_PING_OPEN_CONNECTIONS (0x1C)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x1c	Ping ID	int64	0x00000000003c6d0d	Time since start in Milliseconds
	Server ID	int64	0x00000000372cdc9e
	MAGIC	MAGIC
	Host Info	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. It may be either a 0x1d or a 0x1c, depending on version. If the Server is invisible, this packet will be sent without username)

Unknown (0x84)

Two-Way

Fields in this packet are variable, also the lenght

Packet ID	Field Name	Field Type	Example	Notes
0x84	Unknown	variable
	Total Size:	28 Bytes

Sent after 0x08, and 0xC0

Unknown (0xC0)

Two-Way

Packet ID	Field Name	Field Type	Example	Notes
0xC0	Ping ID	6 bytes	0x000101000000
	Total Size:	7 Bytes

Sent by the Client after the first 0x84. Then, the Server replies with the same packet