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ReversingRakNet.md

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About

RakNet is the C++ library Facepunch uses for network communication to/from the client/server. However the RakNet version used in the game (client) as well in the server is heavily modified since RakNet is open-source.
RakNet is the "legacy" method of networking, the newer method is SteamNetworking but as of writing this, that method is rarely used, its only used if you enable it manually with a launch option.

Overview

Exported DLL functions

  • NETRCV_Address
  • NETRCV_GUID
  • NETRCV_LengthBits
  • NETRCV_Port
  • NETRCV_RawData
  • NETRCV_ReadBytes
  • NETRCV_SetReadPointer
  • NETRCV_UnreadBits
  • NETSND_Broadcast
  • NETSND_ReadCompressedFloat
  • NETSND_ReadCompressedInt32
  • NETSND_ReadCompressedInt64
  • NETSND_Send
  • NETSND_Size
  • NETSND_Start
  • NETSND_WriteBytes
  • NETSND_WriteCompressedFloat
  • NETSND_WriteCompressedInt32
  • NETSND_WriteCompressedInt64
  • NET_Close
  • NET_CloseConnection
  • NET_Create
  • NET_GetAddress
  • NET_GetAveragePing
  • NET_GetGUID
  • NET_GetLastPing
  • NET_GetLowestPing
  • NET_GetReceiveBufferSize
  • NET_GetStatistics
  • NET_GetStatisticsString
  • NET_LastStartupError
  • NET_LimitBandwidth
  • NET_Receive
  • NET_SendMessage
  • NET_StartClient
  • NET_StartServer

Function definitions

NETRCV_Address

Parameters: void* net
Returns: uint32_t

Description: Returns (uint32_t) RakNetStruct+8]+PacketStruct+4]. This is the address of the client/server, the one you started listening on. 16777343 means 127.0.0.1 which is the loopback address, the value 16777343 is 4 byte number from which each byte is the octed of the IP address
See structure image below
img

NETRCV_GUID

Parameters: void* net
Returns: uint64_t

Description: Returns (uint64_t) RakNetStruct+8]+PacketStruct+18]. GUID should be unique per every raknet instance, they might collide across different processes/instances
See structure image below
img

NETRCV_LengthBits

Parameters: void* net
Returns: int

Description: Returns (uint32_t) RakNetStruct+130]. This is how much bits are received from the last call to NET_Receive()
img

NETRCV_Port

Parameters: void* net
Returns: uint32_t

Description: Returns (uint16_t) RakNetStruct+8]+PacketStruct+2]. Again this should be the local port, but its not the correct port, its some other port
See structure image below
img

NETRCV_RawData

Parameters: void* net
Returns: void*

Description: Returns (void*) RakNetStruct+140]. This is a pointer to the data which starts at RakNetStruct+149 which is at the end of the RakNetStruct (this seems to not be true after a while/the initialization)
img

NETRCV_ReadBytes

Parameters: void* net, void* data, int length
Returns: bool

Description: ...

NETRCV_SetReadPointer

Parameters: void* net, int bitsOffset
Returns: void

Description: ...

NETRCV_UnreadBits

Parameters: void* net
Returns: int

Description: (uint32_t) RakNetStruct+138] - NETRCV_LengthBits() if this is == NETRCV_LengthBits() then just NETRCV_LengthBits() is returned

NETSND_Broadcast

Parameters: void* net, int priority, int reliability, int channel
Returns: uint32_t

Description: ...

NETSND_ReadCompressedFloat

Parameters: void* net
Returns: float

Description: ...

NETSND_ReadCompressedInt32

Parameters: ?
Returns: ?

Description: ...

NETSND_ReadCompressedInt64

Parameters: ?
Returns: ?

Description: ...

NETSND_Send

Parameters: void* net, uint64_t connectionID, int priority, int reliability, int channel
Returns: uint32_t

Description: ...

NETSND_Size

Parameters: void* net
Returns: uint32_t

Description: ...

NETSND_Start

Parameters: void* net
Returns: void

Description: ...

NETSND_WriteBytes

Parameters: void* net, void* data, int length
Returns: void

Description: ...

NETSND_WriteCompressed

Parameters: ?
Returns: ?

Description: ...

NETSND_WriteCompressed

Parameters: ?
Returns: ?

Description: ...

NETSND_WriteCompressed

Parameters: ?
Returns: ?

Description: ...

NET_Close

Parameters: void* net
Returns: void

Description: ...

NET_CloseConnection

Parameters: void* net, uint64_t connectionID
Returns: void

Description: ...

NET_Create

Parameters: none
Returns: void* - Ptr to raknetstruct

Description: Creates heap allocated block of 0x250 bytes. Some values are initialized to 0, 2048 and 1.
Image of how the structure looks in ReClass (name of fields are what they are initialized to)
img

NET_GetAddress

Parameters: void* net, uint64_t connectionID
Returns: void*

Description: ...

NET_GetAveragePing

Parameters: void* net, uint64_t connectionID
Returns: int

Description: ...

NET_GetGUID

Parameters: ?
Returns: ?

Description: ...

NET_GetLastPing

Parameters: void* net, uint64_t connectionID
Returns: int

Description: ...

NET_GetLowestPing

Parameters: void* net, uint64_t connectionID
Returns: int

Description: ...

NET_GetReceiveBufferSize

Parameters: void* net
Returns: uint32_t

Description: ...

NET_GetStatistics

Parameters: void* net, uint64_t connectionID, RaknetStats* data, int dataLength
Returns: bool

Description: ...

NET_GetStatisticsString

Parameters: void* net, uint64_t connectionID
Returns: void*

Description: ...

NET_LastStartupError

Parameters: void* net
Returns: void*

Description: ...

NET_LimitBandwidth

Parameters: ?
Returns: ?

Description: ...

NET_Receive

Parameters: void* net
Returns: bool

Description: ...

NET_SendMessage

Parameters: void* net, void* data, int length, uint32_t adr, uint16_t port
Returns: void

Description: ...

NET_StartClient

Parameters: void* net, char* hostName, int port, int retries, int retryDelay, int timeout
Returns: int

Description: ...

NET_StartServer

Parameters: void* net, char* ip, int port, int maxConnections
Returns: int

Description: Initializes structures and copies ip, port and maxConnections to internal structures
NOTE: If IP is empty string it seems it binds to 0.0.0.0 which is just binding to any available IP. Usually this will be computer's IP (like: 192.168.0.170)

(not applicable to all packets, still researching)
(minecraft raknet wiki seems to be accurate to some extent)

UDP frame

addr description
0 raknet packet type
1 sequence number (packet id)
4 msg flags
5 payload len in bits
7 data ...