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	0x0000000000301dfb	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
0x05	MAGIC	MAGIC
	Server ID	int64		This value seems to be constant for an installation of PM, or differs between the demo and full version.
	Unused	byte	0
	Null Payload Lenght	short	1447	Lenght of Null Payload in 0x05. Used to determine packet loss and max UDP packet size
	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	Always 0x043f57fefd
	Port	short	19132
	MTU Size	short	1464
	Client ID	int64	1061862405
	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
	Client ID	int64	0xffffffff
	Unused	5 bytes	0x043f57fefd
	Total Size:	30 Bytes

Sent from server in response to packet 0x07.

ID_ADVERTISE_SYSTEM (0x1d)

See 0x1c

ID_UNCONNECTED_PING_OPEN_CONNECTIONS (0x1c)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x1c	Ping ID	int64	0x0000000000301dfb	Time since start in Milliseconds
	Server ID	int64
	MAGIC	MAGIC
	Host Info	string	MCCPP;Demo;Steve	Used to send the 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.

Unknown (0x84)

Client to Server

Packet ID	Field Name	Field Type	Example	Notes
0x84	Count	byte	2	Count of 0x84 packets sent
	Unknown	9 bytes	Only seen 0x000040009000000009	Unknown, could be split in more fields
	Unknown	int	Only seen 0xffffffff
	Session ID?	int	0xb2e9b623	Same as last field of 0x07
	Unknown	5 bytes	Only seen 0x0000000000
	Unknown	4 bytes	0xa6b42b00	Last byte only seen as 0x00
	Total Size:	28 Bytes

Sent after 0x08. The client will send 5 0x84 packets, incrementing the count every time (starting at 0)