DSR Steam Communication

This handles setting up/closing down connections, voice packets, other steam management stuff.

Reading https://partner.steamgames.com/doc/api may be helpful.

The two primary functions of interest are

void GetSteamData_Packet(DLNRD::SteamSessionLight *SteamSessionLight, DLNRD::SteamSessionMemberLight *SteamSessionMemberLight, uint param_3,uint8_t *data, uint data_len) @141088020

and 
SendSteamData_Packet1 @1410B3F58
SendSteamData_Packet2 @1410B58DC
SendSteamData_Packet3 @1410B584C
(the type is stored in the byte at data+6 at this point)

For sending SteamData packets, the send function must be queued as a task in the SteamSession. This is done by SteamSessionLight_Queue_SendSteamMessage @14109cfd0.

For steam callbacks, you want to get the callback functions from the DLNRD::SteamSurveillance class, created by Init_DLNRD::SteamSurveillance @14107b750, and it's accessed by a global pointer at 141da1ab0.

Packet Types

This list is a Work-In-Progress. Underlined types are fully understood.
The functions which handle each type are labeled sendTypeXSteamMessage and readparseTypeXSteamMessage

Prolog for all packets:

char magic[4] = "VRXN";
uint16_t header = 0x584;
uint8_t type

(note this is converted to big endian before sending)

4. SessionPropertyReq

9. SyncSessionMemberRequest1

10. SyncSessionMemberRequest2

  • Regularly sent every few frames from the host to the guests
  • Contains a byte with the number of players the host sees present the world
  • Followed by each player's steam name, separated by 0x7

11. SendHostSearchResponse

12. P2PCommunicationResponse

  • First packet sent on start of session communication/initialization
  • Doesn't contain any data

13. OnAuthTicket

15. Response sent by guest to type 46 packet

24. SessionProperties

29. StartGame

30. CreateSessionVisibleTask

31. CreateSessionInvisibleTask

34. SyncSessionMemberResponse

  • Send as a response to type 10 from the guest to the host
  • Contains the number of players that are present in the type 10 packet but NOT present in the guest's world
  • If this value is >0 for a certain amount of time, the host will disconnect the guest with a 0xff000020 kickout reason
  • A desync detection and prevention measure

35. SearchHostResponse

36. ReceiveRandomNumber

  • Response automatically sent to type 12
  • optional dword of data

37. SyncSessionMemberRequest3

38. Response packet sent by host upon receiving type 15

42. NotifyLeavePlayer

46. KickOutTask

  • Packet requesting that you leave the session
  • data = uint32_t //usually 0xff000019

49. Unk2

50. LeaveMember