Minecraft:RakNet

RakNet<ref>http://www.jenkinssoftware.com/</ref> is a networking library and protocol for multiplayer games. It runs over UDP and provides connection management, configurable reliability and ordering, sequencing, and fragmentation.

UDP does not guarantee delivery or ordering. RakNet supports different delivery modes, so applications can request reliability or ordering when needed.

The source code for RakNet is available in the OculusVR archive.

Use in Bedrock Edition

In Minecraft:Bedrock Edition, Minecraft:NetherNet became the default transport for dedicated servers in Minecraft:26.50. RakNet is deprecated in the Minecraft:26.60.22 Preview.

Libraries

Here is an incomplete list of RakNet libraries. Their supported features and protocol versions may differ, so check each project's documentation for compatibility.

Name	Description	Language	License
go-raknet	RakNet implementation used by Dragonfly.	Go	MIT
RakNet	Asynchronous RakNet implementation written in Rust.	Rust	Apache-2.0
PieRakNet	RakNet implementation written in Python for PieMC.	Python	GPL-3.0
Cloudburst Network	Network components used by CloudburstMC projects.	Java	Apache-2.0
rak-net	Python RakNet implementation originally developed for Podrum.	Python	GPL-2.0
JRakNet	Java implementation of the RakNet protocol.	Java	MIT
netty-raknet	RakNet implementation for Netty.	Java	MIT
JRakLibPlus	RakNet server library based on RakLib and JRakLib.	Java	LGPL
RakLib	Lightweight PHP RakNet server implementation.	PHP	GPL-3.0
raknet	UDP networking library for Node.js that follows the RakNet protocol.	JavaScript	MIT
PyRakLib	Python port of RakLib that follows the RakNet protocol.	Python	GPL
rust-raknet	RakNet implementation written in Rust.	Rust	MIT
Baltica	Bedrock toolkit that includes a RakNet implementation.	TypeScript	See repository
RakNet.Py	RakNet protocol version 5 implementation for older MCPE versions.	Python	GPL
LavishMC RakNet	C++ fork of the original RakNet implementation.	C++	BSD
RakNet (original)	Original C++ RakNet implementation.	C++	BSD-2-Clause

Data types

RakNet packet fields use fixed-width integers and a few protocol-specific types. Byte order depends on the field; use the packet definition when encoding or decoding multi-byte values.<ref>RakNet: BitStream GolemOrg: RakNet protocol notes</ref>

Type	Size	Description
Byte	1 byte	Unsigned 8-bit value.
Boolean	1 byte	Template:Cd is false; Template:Cd is true.
Short	2 bytes	Signed 16-bit integer.
Unsigned Short	2 bytes	Unsigned 16-bit integer.
Int	4 bytes	Signed 32-bit integer.
Long	8 bytes	64-bit integer. Whether it represents a signed value depends on the field.
uint24le	3 bytes	Unsigned 24-bit little-endian integer, used for frame sequence numbers.
String	Variable	In RakNet string fields, an unsigned 16-bit length precedes the string bytes.
Magic	16 bytes	The fixed Template:Cd value used in offline packets.<ref>RakNet: RakPeer.cpp</ref>
Address	7 bytes (IPv4); 29 bytes (IPv6)	Encodes the address family, address and port. IPv4 address bytes are inverted; the port is big-endian. IPv6 also includes address-family, flow-info and scope fields.<ref name="address-format">GolemOrg: RakNet address format</ref>

Handshake sequence

RakNet establishes a peer connection first, then completes the connection with the application.<ref>RakNet: RakPeer.cpp GolemOrg: RakNet connection sequence</ref>

1. C→S: Open Connection Request 1
2. S→C: Open Connection Reply 1 (or Incompatible Protocol)
3. C→S: Open Connection Request 2
4. S→C: Open Connection Reply 2. The RakNet peer connection is established.
5. C→S: Connection Request
6. S→C: Connection Request Accepted
7. C→S: New Incoming Connection

After this exchange, peers can send connected packets. In Minecraft:Bedrock Edition, game packets are carried in RakNet frames as described at Game Packet.

Packets

Packet identifiers below follow the standard RakNet packet IDs. Some field details vary by implementation.<ref>RakNet: Message identifiers GolemOrg: RakNet protocol notes</ref>

Unconnected Ping

Packet ID	Field Name	Field Type	Notes
0x01, 0x02	Time	Long
	MAGIC	magic
	Client GUID	Long

The client sends this packet to discover a server. ID Template:Cd is a regular unconnected ping; Template:Cd asks for a response only when the server has open connections. The server replies with Unconnected Pong.

Unconnected Pong

Packet ID	Field Name	Field Type	Notes
0x1c	Time	Long
	Server GUID	Long
	MAGIC	magic
	Server ID String	string	Carries server-list information.

The server sends this in response to an unconnected ping. It echoes the ping time and includes its GUID and a server ID string. In Minecraft:Bedrock Edition, that string contains server-list information in a semicolon-delimited format; its fields can vary by game version.

Connected Ping

Packet ID	Field Name	Field Type	Notes
0x00	Time	Long

This packet measures latency on an established connection. It is commonly sent unreliably.

Connected Pong

Packet ID	Field Name	Field Type	Notes
0x03	Ping Time	Long
	Pong Time	Long

The receiver replies with the original ping time and its own response time. It is commonly sent unreliably.

Open Connection Request 1

The first packet in the handshake sequence, sent by the client to the server.

Packet ID	Field Name	Field Type	Notes
0x05	Magic	MAGIC
	Protocol version	byte	RakNet protocol version used by the client.
	MTU	Zero padding	Zero padding used to probe the path MTU.

The padding is used to probe the path MTU. The server replies with the selected MTU, or sends Incompatible Protocol if it does not support the client's RakNet protocol version.

Open Connection Reply 1

The second packet in the handshake sequence, sent by the server to the client.

Packet ID	Field Name	Field Type	Notes
0x06	Magic	MAGIC
	Server GUID	Long
	Use security	boolean	Indicates whether the server is using RakNet's security challenge.
	Cookie	Int	Present only when security is enabled; returned by the client in Open Connection Request 2.
	MTU	Unsigned short	Selected MTU for the connection.

Open Connection Request 2

The third packet in the handshake sequence, sent by the client to the server.

Packet ID	Field Name	Field Type	Notes
0x07	Magic	MAGIC
	Cookie	Int	Present only when the server provided a cookie.
	Has security challenge	boolean	Sent with the cookie when security is enabled.
	Server Address	address
	MTU	Unsigned Short
	Client GUID	Long

Open Connection Reply 2

The fourth packet in the handshake sequence, sent by the server to the client.

Packet ID	Field Name	Field Type	Notes
0x08	Magic	MAGIC
	Server GUID	Long
	Client Address	address
	MTU	Unsigned Short
	Encryption enabled	boolean

Connection Request

The client sends this packet after the RakNet peer connection is established to request an application-level connection.

Packet ID	Field Name	Field Type	Notes
0x09	GUID	Long
	Time	Long
	Use security	boolean

Connection Request Accepted

The server sends this packet to accept the client's connection request.

Packet ID	Field Name	Field Type	Notes
0x10	Client address	address
	System index	Unsigned Short	System index assigned by the server.
	Internal addresses	10x address	Internal server addresses.
	Request time	Long	Shall be the corresponding timestamp of the Connection Request
	Time	Long	Server acceptance time.

New Incoming Connection

The client sends this packet to confirm that it received the server's acceptance.

Packet ID	Field Name	Field Type	Notes
0x13	Server address	address
	Internal addresses	20x address	Internal client addresses.
	Incoming Timestamp	Long
	Server Timestamp	Long

Disconnection Notification

This packet notifies the other peer that the sender is disconnecting

Packet ID	Field Name	Field Type	Notes
0x15	No payload		Signals that the sender is disconnecting.

Incompatible Protocol

The server sends this packet when it does not support the RakNet protocol version used by the client.

Packet ID	Field Name	Field Type	Notes
0x19	Protocol	byte
	Magic	MAGIC
	Server GUID	Long

Frame Set Packet

This packet carries one or more frames between connected peers.

Packet ID	Field Name			Field Type	Notes
0x80..0x8d	Sequence number			uint24le	Used for building ACK and NACK ranges
	Frames	Flags		byte	Top 3 bits give the reliability type, fourth bit is 1 when the frame is fragmented and part of a compound.
		Length IN BITS		unsigned short	Length of the body in bits. Big-endian.
		Reliable frame index		uint24le	Only if reliable, used for detecting frame level duplication
		Sequenced frame index		uint24le	Only if sequenced, used for discarding out-of-date packets
		Order (only if ordered, see below)	Ordered frame index	uint24le	Tells the receiver the correct order in which to deliver frames to the application
			Order channel	byte	Maximum of 32 channels
		Fragment (only if fragmented)	Compound size	Unsigned Int	Total size of the compound
			Compound ID	Unsigned Short	Identifies which compound this fragment is part of
			Index	Unsigned Int	Index of this fragment in the compound
		Body	ceil(length/8) bytes

Note 1: there can be multiple frames in each Frame Set Packet.
Note 2: A packet is a Frame Set Packet if (packet_ID & 0x80) == 0x80 and (packet_ID & 0x60) == 0

The reliability types are as follows:

ID	Name	Reliable	Sequenced	Ordered
0	unreliable
1	unreliable sequenced		x
2	reliable	x
3	reliable ordered	x		x
4	reliable sequenced	x	x
5	unreliable (+ ACK receipt)
6	reliable (+ ACK receipt)	x
7	reliable ordered (+ ACK receipt)	x		x

Sequenced delivery discards older packets when a newer packet has arrived. Ordered delivery preserves the order of reliable packets within a channel.

Game Packet

This packet carries game-protocol data. In Minecraft:Bedrock Edition, its body contains a batch of game packets.

Packet ID	Field Name	Field Type	Notes
0xfe	Body	bytes	In Minecraft:Bedrock Edition, the body contains a batch of game packets. Framing and compression are described in Bedrock Edition protocol.

In Minecraft:Bedrock Edition, the body carries a batch of game packets encoded according to the Minecraft:Bedrock Edition protocol. See Bedrock Edition protocol/Packets for their definitions.

NACK

This packet reports datagrams that were not received so the sender can retransmit them when required.

Packet ID	Field Name			Field Type	Notes
0xa0	Record count			Unsigned Short	Number of records in the packet
	Records	Is Single?		boolean	False for range, True for no range
		No Range, if is_single == true	Sequence number	uint24le	Datagram sequence number in this record.
		Range, if is_single == false	Start Sequence number	uint24le	First datagram sequence number in the range.
			End Sequence number	uint24le	Last datagram sequence number in the range.

A NACK reports frame-set sequence numbers that were not received, prompting retransmission where required.

ACK

This packet acknowledges datagrams received from the other peer.

Packet ID	Field Name			Field Type	Notes
0xc0	Record count			Unsigned Short	Number of records in the packet
	Records	Is Single?		boolean	False for range, True for no range
		No Range, if is_single == true	Sequence number	uint24le	Datagram sequence number in this record.
		Range, if is_single == false	Start Sequence number	uint24le	First datagram sequence number in the range.
			End Sequence number	uint24le	Last datagram sequence number in the range.

An ACK reports frame-set sequence numbers that were received. Both ACK and NACK packets can contain multiple records.