Network documentation
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Header
All of SRB2's packets start out with a specific 8-byte header, consisting of four values and a padding byte:
Data name | Data type | Description |
---|---|---|
checksum
|
Unsigned 32-bit Integer | The checksum. |
ack
|
Unsigned 8-bit Integer | The acknowledgment variable. If not null, the server must send whatever is contained here in the next part of the header structure. |
ackreturn
|
Unsigned 8-bit Integer | The acknowledgment variable's return. |
packettype
|
Unsigned 8-bit Integer | The packet type. |
reserved
|
Null byte | Padding. |
Checksum calculation
The checksum for all packets is calculated in the function named NetbufferChecksum. This checksum is analyzed when the server receives the packet, and if it does not match what the server is expecting, it discards the packet without a reply.
List of packet types
Decimal ID | Hex ID | Name | Sender → receiver | Purpose |
---|---|---|---|---|
0 | 0x00
|
PT_NOTHING
|
Server → Client Client → Server |
Sends a no-op through the network. |
1 | 0x01
|
PT_SERVERCFG
|
Server → Client | Sends server configuration to the client. Is considered a positive response to a request to join the server. |
2 | 0x02
|
PT_CLIENTCMD
|
Client → Server | Contains a client's ticcmd. |
3 | 0x03
|
PT_CLIENTMIS
|
Client → Server | Contains a client's ticcmd. Is used when the server missed a ticcmd and the client is sending it again. |
4 | 0x04
|
PT_CLIENT2CMD
|
Client → Server | Contains two clients' ticcmds for splitscreen. |
5 | 0x05
|
PT_CLIENT2MIS
|
Client → Server | Contains two clients' ticcmds for splitscreen. Is used when the server missed a ticcmd and the clients are sending it again. |
6 | 0x06
|
PT_NODEKEEPALIVE
|
Client → Server | Sent to the server to tell that the client is still alive but has nothing to send for this tic. |
7 | 0x07
|
PT_NODEKEEPALIVEMIS
|
Client → Server | Sent to the server to tell that the client is still alive but has nothing to send for this tic. Is used when the server missed a ticcmd and the client is sending it again. |
8 | 0x08
|
PT_SERVERTICS
|
Server → Client | Server sending all the clients' ticcmds and net commands to each other. |
9 | 0x09
|
PT_SERVERREFUSE
|
Server → Client | Sends a refusal notice to a client that wishes to connect, which contains a reason. |
10 | 0x0A
|
PT_SERVERSHUTDOWN
|
Server → Client | Sent when the server shuts down, disconnecting all clients in the process. |
11 | 0x0B
|
PT_CLIENTQUIT
|
Client → Server | Sent when a client disconnects from the server. |
12 | 0x0C
|
PT_ASKINFO
|
Client → Server | Sent when a client requests info from a server. |
13 | 0x0D
|
PT_SERVERINFO
|
Server → Client | Sent by the server as one of two replies to PT_ASKINFO . Contains server information.
|
14 | 0x0E
|
PT_PLAYERINFO
|
Server → Client | Sent by the server as the other one of two replies to PT_ASKINFO . Contains information on all players in the server.
|
15 | 0x0F
|
PT_REQUESTFILE
|
Client → Server | Sent by the client to request the transfer all important files from the server that they do not already have. If the client has a different version of any needed file (the MD5 sum is bad), the file will also be requested here. |
16 | 0x10
|
PT_ASKINFOVIAMS
|
N/A | Unused – this packet appears to have been identical to PT_ASKINFO , except it tells the server to send PT_SERVERINFO /PT_PLAYERINFO packets to the IP address contained in the packet. However, nothing is designed to send this packet type anymore, if ever at all, so it should be considered obsolete.
|
17 | 0x11
|
PT_WILLRESENDGAMESTATE
|
Server → Client | "Hey Client, I am about to resend you the gamestate!" |
18 | 0x12
|
PT_CANRECEIVEGAMESTATE
|
Client → Server | "Okay Server, I'm ready to receive it, you can go ahead." |
19 | 0x13
|
PT_RECEIVEDGAMESTATE
|
Client → Server | "Thank you Server, I am ready to play again!" |
20 | 0x14
|
PT_SENDINGLUAFILE
|
Server → Client | Server telling a client Lua needs to open a file |
21 | 0x15
|
PT_ASKLUAFILE
|
Client → Server | Client telling the server they don't have the file |
22 | 0x16
|
PT_HASLUAFILE
|
Client → Server | Client telling the server they have the file |
23 | 0x17
|
PT_CANFAIL
|
The packet types below this line can fail to be sent. In addition, these packet types can't occupy all the available ack slots. | |
23 | 0x17
|
PT_FILEFRAGMENT
|
Server → Client | A fragment of a file sent by the server to the client. This is either a fragment of an important file sent in reply to PT_REQUESTFILE , or a fragment of $$$.sav (the netgame's savefile).
|
24 | 0x18
|
PT_FILEACK
|
||
25 | 0x19
|
PT_FILERECEIVED
|
||
26 | 0x1A
|
PT_TEXTCMD
|
Client → Server | Extra net commands from the client, e.g. SAY commands. |
27 | 0x1B
|
PT_TEXTCMD2
|
Client → Server | Extra net commands from a splitscreen client. |
28 | 0x1C
|
PT_CLIENTJOIN
|
Client → Server | Sent by a client to request to join a server. |
29 | 0x1D
|
PT_NODETIMEOUT
|
Server/Client → self | Sent by a client or server, to themselves, to indicate to the game that a client has lost connection to the server. |
30 | 0x1E
|
PT_LOGIN
|
Client → Server | Sent by a client to attempt a login. If successful, the player is awarded admin privileges. This is sent when a player uses the login command.
|
31 | 0x1F
|
PT_PING
|
Server → Client | Sent by the server to inform a client of all the other clients' pings. |
Network documentation | [view] | |
Packet types | PT_ASKINFO • PT_SERVERINFO • PT_PLAYERINFO
| |
Other | Net commands |