Launcher protocol

This launcher protocol lets you to talk to servers and get information from them, allowing you to make your own custom programs like browsers, stat tools, and so on.

Protocol information

See "article history" to look up the protocol for prior versions.

The basics

All Zandronum servers use UDP as their network protocol. Additionally, all traffic is compressed using the Huffman algorithm to save bandwidth. Refer to code in src/huffman for a standalone implementation of the Huffman encoding needed to encode/decode traffic.

Definition of data types used in this article:

• Byte: 8 bit integer
• Short: 16 bit integer
• Long: 32 bit integer
• Float: Long representation of a float
• String: null-terminated series of Bytes

Traffic is encoded in little-endian.

Getting the list of servers

This is very easy, accomplished by sending a long and a short to the master server:

Type	Value	Description
Long	5660028	LAUNCHER_MASTER_CHALLENGE
Short	2	MASTER_SERVER_VERSION

If your request is denied, the server will respond with one of the following:

Type	Value	Description
Long	3	Denied; your IP is banned (MSC_IPISBANNED)
Long	4	Denied; your IP has made a request in the past 3 seconds (MSC_REQUESTIGNORED)
Long	5	Denied; you're using an older version of the master protocol (MSC_WRONGVERSION)

If you are accepted, you will receive multiple packets, each starting with:

Type	Value	Description
Long	6	Beginning of list (MSC_BEGINSERVERLISTPART)
Byte	0-255	Packet number (starting with 0)
Byte	8	Beginning of server block (MSC_SERVERBLOCK)

Then you will get this next block, which is repeated for every IP with servers on it.

Type	Value	Description
Byte	0-255	n = Number of servers with this IP address
Byte	0-255	IP address octet
Byte	0-255	IP address octet
Byte	0-255	IP address octet
Byte	0-255	IP address octet
Short	0-65535	IP port (sent 'n' times)

Once the packet is full or all servers are transferred, you will receive 0 as number of servers on the next IP.

Type	Value	Description
Byte	0	There are no ports for the next server, i.e. no more servers in this packet.

Finally, the response should end with either

Type	Value	Description
Byte	2	End of list, you got the full server list now (MSC_ENDSERVERLIST)

or

Type	Value	Description
Byte	7	End of current part of the list, you'll get more packets (MSC_ENDSERVERLISTPART)

Querying individual servers

You need to choose what data you'd like. To do so, bitshift the combination of flags with a boolean OR. For example, to get the server's name and player count, you'd use (SQF_NAME|SQF_NUMPLAYERS). Use these flags appropriately; doing so saves your users' and server hosters' bandwidth.

Query flags

Name	Value	Description
SQF_NAME	0x00000001	The name of the server
SQF_URL	0x00000002	The associated website
SQF_EMAIL	0x00000004	Contact address
SQF_MAPNAME	0x00000008	Current map being played
SQF_MAXCLIENTS	0x00000010	Maximum amount of clients who can connect to the server
SQF_MAXPLAYERS	0x00000020	Maximum amount of players who can join the game (the rest must spectate)
SQF_PWADS	0x00000040	PWADs loaded by the server
SQF_GAMETYPE	0x00000080	Game type code
SQF_GAMENAME	0x00000100	Game mode name
SQF_IWAD	0x00000200	The IWAD used by the server
SQF_FORCEPASSWORD	0x00000400	Whether or not the server enforces a password
SQF_FORCEJOINPASSWORD	0x00000800	Whether or not the server enforces a join password
SQF_GAMESKILL	0x00001000	The skill level on the server
SQF_BOTSKILL	0x00002000	The skill level of any bots on the server
SQF_DMFLAGS	0x00004000	(Deprecated) The values of dmflags, dmflags2 and compatflags. Use SQF_ALL_DMFLAGS instead.
SQF_LIMITS	0x00010000	Timelimit, fraglimit, etc.
SQF_TEAMDAMAGE	0x00020000	Team damage factor.
SQF_TEAMSCORES	0x00040000	(Deprecated) The scores of the red and blue teams. Use SQF_TEAMINFO_* instead.
SQF_NUMPLAYERS	0x00080000	Amount of players currently on the server.
SQF_PLAYERDATA	0x00100000	Information of each player in the server.
SQF_TEAMINFO_NUMBER	0x00200000	Amount of teams available.
SQF_TEAMINFO_NAME	0x00400000	Names of teams.
SQF_TEAMINFO_COLOR	0x00800000	RGB colors of teams.
SQF_TEAMINFO_SCORE	0x01000000	Scores of teams.
SQF_TESTING_SERVER	0x02000000	Whether or not the server is a testing server, also the name of the testing binary.
SQF_DATA_MD5SUM	0x04000000	(Deprecated) Used to retrieve the MD5 checksum of skulltag_data.pk3, now obsolete and returns an empty string instead.
SQF_ALL_DMFLAGS	0x08000000	Values of various dmflags used by the server.
SQF_SECURITY_SETTINGS	0x10000000	Security setting values (for now only whether the server enforces the master banlist)
SQF_OPTIONAL_WADS	0x20000000	Which PWADs are optional
SQF_DEH	0x40000000	List of DEHACKED patches loaded by the server.
SQF_EXTENDED_INFO	0x80000000	Additional server information, see the table below for more information.

Extended flags

Name	Value	Description
SQF2_PWAD_HASHES	0x00000001	The MD5 hashes of the server's loaded PWADs.
SQF2_COUNTRY	0x00000002	The server's ISO 3166-1 alpha-3 country code.
SQF2_GAMEMODE_NAME	0x00000004	(development version 3.2-alpha and above only) The name of the server's current game mode.
SQF2_GAMEMODE_SHORTNAME	0x00000008	(development version 3.2-alpha and above only) The short name of the server's current game mode.

Segmented challenge

(development version 3.2-alpha and above only)

This challenge is only available on servers running Zandronum 3.2 or newer. For backwards compatibility, the old #Old protocol is still supported and can also request a segmented response, but is now deprecated. It is recommended that launchers prefer this new challenge when 3.2 reaches widespread adoption and fall back to the old challenge.

Type	Value	Description
Long	200	Launcher challenge
Long	Flags	Desired information
Long	Time	Current time, this will be sent back to you so you can determine ping.
Long	Flags2	The extended information you want. Ensure you specify SQF_EXTENDED_INFO in the normal Flags field as well.

The server will respond with a Long, which will be one of the following:

Symbol	Value	Description
SERVER_LAUNCHER_IGNORING	5660024	Denied; your IP has made a request in the past sv_queryignoretime seconds
SERVER_LAUNCHER_BANNED	5660025	Denied; your IP is banned
SERVER_LAUNCHER_SEGMENTED_CHALLENGE	5660031	Accepted; segmented information follows

If you were denied, this response is followed by another Long, which is the time you sent to the server.

Old protocol challenge

Send the server the following packet:

Type	Value	Description
Long	199	Launcher challenge
Long	Flags	Desired information
Long	Time	Current time, this will be sent back to you so you can determine ping.
Long	Flags2	Optional. The extended information you want. Ensure you specify SQF_EXTENDED_INFO in the normal Flags field as well.
Byte	Segmented	Optional. Set this to 1 to indicate that you want a segmented response. This exists for backwards compatibility with older servers.

The server will respond with a Long, which will be one of the following:

Symbol	Value	Description
SERVER_LAUNCHER_CHALLENGE	5660031	Accepted; server information follows
SERVER_LAUNCHER_IGNORING	5660024	Denied; your IP has made a request in the past sv_queryignoretime seconds
SERVER_LAUNCHER_BANNED	5660025	Denied; your IP is banned
SERVER_LAUNCHER_SEGMENTED_CHALLENGE	5660031	Accepted; segmented information follows

Segmented protocol response

If you asked for a segmented response, and the server supports it, you'll get:

Type	Value	Description
Byte	Segment	Segment number. If the most significant bit is set, then this is the last segment.
Short	Size	The uncompressed size of this packet.

After this, segment 0 also includes:

Type	Value	Description
Long	Time	The time you sent to the server.
String	Version	Server version string with revision number.

Each field set returned then contains the following information before the actual data.

Type	Value	Description
Byte	Fieldset	The field set this packet contains data for (0 -> SQF_, 1 -> SQF2_)
Long	Flags	The fields contained in this packet.

Single packet response

If you didn't ask for a segmented response, or the server doesn't support segmented packets, you'll get:

Type	Value	Description
Long	Time	The time you sent to the server.
String	Version	Server version string with revision number.
Long	Flags	The info you'll be receiving, possibly corrected (see below).

Field data

Field data is sent in the order the fields appear in the table below. The server will automatically correct your request if you made a mistake (like request team scores in cooperative games), so always use the flags it sends back to you when reading your data.

Flag set 0 (SQF_)

Type	Flag	Description
String	SQF_NAME	The server's name (sv_hostname)
String	SQF_URL	The server's WAD URL (sv_website)
String	SQF_EMAIL	The server host's e-mail (sv_hostemail)
String	SQF_MAPNAME	The current map's name
Byte	SQF_MAXCLIENTS	The max number of clients (sv_maxclients)
Byte	SQF_MAXPLAYERS	The max number of players (sv_maxplayers)
Byte	SQF_PWADS	The number of PWADs loaded
String	SQF_PWADS	The PWAD's name (Sent for each PWAD)
Byte	SQF_GAMETYPE	The current game mode. See below.
Byte	SQF_GAMETYPE	Instagib - true (1) / false (0)
Byte	SQF_GAMETYPE	Buckshot - true (1) / false (0)
String	SQF_GAMENAME	The base game's name ("DOOM", "DOOM II", "HERETIC", "HEXEN", "ERROR!")
String	SQF_IWAD	The IWAD's name
Byte	SQF_FORCEPASSWORD	Whether a password is required to join the server (sv_forcepassword)
Byte	SQF_FORCEJOINPASSWORD	Whether a password is required to join the game (sv_forcejoinpassword)
Byte	SQF_GAMESKILL	The game's difficulty (skill)
Byte	SQF_BOTSKILL	The bot difficulty (botskill)
Long	SQF_DMFLAGS	[Deprecated] Value of dmflags
Long	SQF_DMFLAGS	[Deprecated] Value of dmflags2
Long	SQF_DMFLAGS	[Deprecated] Value of compatflags
Short	SQF_LIMITS	Value of fraglimit
Short	SQF_LIMITS	Value of timelimit
Short	SQF_LIMITS	time left in minutes (only sent if timelimit > 0)
Short	SQF_LIMITS	duellimit
Short	SQF_LIMITS	pointlimit
Short	SQF_LIMITS	winlimit
Float	SQF_TEAMDAMAGE	The team damage scalar (teamdamage)
Short	SQF_TEAMSCORES	[Deprecated] Blue team's fragcount/wincount/score
Short	SQF_TEAMSCORES	[Deprecated] Red team's fragcount/wincount/score
Byte	SQF_NUMPLAYERS	The number of players in the server
Byte	SQF_PLAYERDATA	Segmented only: Whether the team field for each player is sent. Unlike all other fields for SQF_PLAYERDATA, this is only sent once, and not for each player.
String	SQF_PLAYERDATA	Player's name
Short	SQF_PLAYERDATA	Player's pointcount/fragcount/killcount
Short	SQF_PLAYERDATA	Player's ping
Byte	SQF_PLAYERDATA	Player is spectating - true (1) / false (0)
Byte	SQF_PLAYERDATA	Player is a bot - true (1) / false (0)
Byte	SQF_PLAYERDATA	Player's team (returned on team games, 255 is no team)
Byte	SQF_PLAYERDATA	Player's time on the server, in minutes. Note: SQF_PLAYERDATA information is sent once for each player on the server.
Byte	SQF_TEAMINFO_NUMBER	The number of teams used.
String	SQF_TEAMINFO_NAME	The team's name. (Sent for each team.)
Long	SQF_TEAMINFO_COLOR	The team's color. (Sent for each team.)
Short	SQF_TEAMINFO_SCORE	The team's score. (Sent for each team.)
Byte	SQF_TESTING_SERVER	Whether this server is running a testing binary - true (1) / false (0)
String	SQF_TESTING_SERVER	An empty string in case the server is running a stable binary, otherwise name of the testing binary archive found in http://www.skulltag.com/testing/files/
String	SQF_DATA_MD5SUM	[Deprecated] Returns an empty string.
Byte	SQF_ALL_DMFLAGS	The number of flags that will be sent.
Long	SQF_ALL_DMFLAGS	The value of the flags (Sent for each flag in the order dmflags, dmflags2, zadmflags, compatflags, zacompatflags, compatflags2)
Byte	SQF_SECURITY_SETTINGS	Whether the server is enforcing the master ban list - true (1) / false (0) The other bits of this byte may be used to transfer other security related settings in the future.
Byte	SQF_OPTIONAL_WADS	Amount of optional wad indices that follow
Byte	SQF_OPTIONAL_WADS	Index number int the list sent with SQF_PWADS - this wad is optional (sent for each optional Wad)
Byte	SQF_DEH	Amount of deh patches loaded
String	SQF_DEH	Deh patch name (one string for each deh patch)
Byte	SQF_EXTENDED_INFO	Segmented protocol: The next flag set you will receive.
Long	SQF_EXTENDED_INFO	Segmented protocol: The flags specifying the information from the next flag set that immediately follows. Old protocol: The flags specifying the SQF2_data that immediately follows.

Flag set 1 (SQF2_)

Type	Flag	Description
Byte	SQF2_PWAD_HASHES	The number of hashes sent.
String	SQF2_PWAD_HASHES	The hash of the PWAD, sent for each PWAD. The indices are the same as sent in SQF_PWADS
Byte[3]	SQF2_COUNTRY	The server's ISO 3166-1 alpha-3 country code. This is sent as a raw char array of 3 length, there is no null terminator. Zandronum also has two special values for this field, XIP and XUN. See #Country codes below for how to handle this field.
String	SQF2_GAMEMODE_NAME	(development version 3.2-alpha and above only) The name of the server's current game mode, as defined in the GAMEMODE lump.
String	SQF2_GAMEMODE_SHORTNAME	(development version 3.2-alpha and above only) The short name of the server's current game mode, as defined in the GAMEMODE lump.

Notes

Game modes

Game modes are defined as:

   0   GAMEMODE_COOPERATIVE
   1   GAMEMODE_SURVIVAL
   2   GAMEMODE_INVASION
   3   GAMEMODE_DEATHMATCH
   4   GAMEMODE_TEAMPLAY
   5   GAMEMODE_DUEL
   6   GAMEMODE_TERMINATOR
   7   GAMEMODE_LASTMANSTANDING
   8   GAMEMODE_TEAMLMS
   9   GAMEMODE_POSSESSION
   10  GAMEMODE_TEAMPOSSESSION
   11  GAMEMODE_TEAMGAME
   12  GAMEMODE_CTF
   13  GAMEMODE_ONEFLAGCTF
   14  GAMEMODE_SKULLTAG
   15  GAMEMODE_DOMINATION

Country codes

Zandronum 3.1 introduces the ability to server hosts to specify the country their server is located in via a new CVAR, sv_country. This was introduced to allow hosts to combat the inaccuracies of IP geolocation that launchers rely on. This value is specified to launchers via the new SQF2_COUNTRY field, which can have the following values:

• an ISO 3166-1 alpha-3 country code. Note that Zandronum doesn't validate whether the country code supplied in sv_country is a registered country code. If the launcher does not recognise the given code, then it should display the server's country as unknown.
• the value XIP, which suggests to the launcher that it should attempt IP geolocation to determine the server's country. The default value of sv_country will cause it to return this by default, to preserve existing behaviour and make it easier for casual hosts. If geolocation is unsupported, disabled, or fails, then the server's country should be displayed as unknown.
• the value XUN, in which case the launcher should display the server's country as unknown.

Also see Issue 3894: Allow servers to present their country to launchers.

Examples

Basic segmented example

In this example we query a simple co-operative server for some basic information.

Request

Type	Value	Description
Long	200	The launcher challenge.
Long	1234	Ping value.
Long	36700161	The fields from set 0 we want: SQF_NAME|SQF_PLAYERDATA|SQF_TEAMINFO_NUMBER|SQF_TESTING_SERVER
Long	6	The fields from set 1 we want: SQF2_COUNTRY|SQF2_GAMEMODE_NAME

Response

Type	Value	Description
Long	5660031	The server's response, indicating we're getting a segmented response packet.
Byte	177	The segment number. The most significant bit is set, as this is the final and only packet. Clear the MSB to reveal this is packet 0: 128 & ~0x80 = 0.
Short	143	Size of this packet in bytes.
Long	1234	The ping value we sent before, sent only in segment 0.
String	3.2-alpha-r230430-1741 on Linux 5.15.0-69-generic	The server version, sent only in segment 0.
Byte	0	The initial flag set being sent.
Long	35127297	The initial flags from that set being sent: SQF_NAME|SQF_NUMPLAYERS|SQF_PLAYERDATA|SQF_TESTING_SERVER|SQF_EXTENDED_INFO. Observe how: SQF_NUMPLAYERS was added by the server as we requested SQF_PLAYERDATA. SQF_EXTENDED_INFO was added indicating we'll get data from another flag set later in this segment. SQF_TEAMINFO_NUMBER was removed as this is a co-operative server and team information is irrelevant.
String	Skipper Pavilion	From SQF_NAME. The server's name.
Byte	1	From SQF_NUMPLAYERS. The number of players online.
Byte	0	From SQF_PLAYERDATA. Whether the team field will be sent for players.
String	Alphus	From SQF_PLAYERDATA. The name of the first player in the server.
Short	0	From SQF_PLAYERDATA. Alphus' score.
Short	0	From SQF_PLAYERDATA. Alphus' ping.
Byte	0	From SQF_PLAYERDATA. Whether Alphus is a spectator or not.
Byte	1	From SQF_PLAYERDATA. Whether Alphus is a bot or not.
Byte	5	From SQF_PLAYERDATA. How many minutes Alphus has been in the server.
Byte	1	From SQF_TESTING_SERVER. Whether the server is running a testing binary.
String	downloads/testing/3.2/ZandroDev3.2-230430-1741windows.zip	From SQF_TESTING_SERVER. Path to the testing binary on zandronum.com.
Byte	1	From SQF_EXTENDED_INFO. The flag set that follows.
Long	6	From SQF_EXTENDED_INFO. The fields that follow from that set: SQF2_COUNTRY|SQF2_GAMEMODE_NAME
char[3]	GBR	From SQF2_COUNTRY. The country code the server presents, as set by sv_country.
String	Cooperative	From SQF2_GAMEMODE_NAME. The name of the game mode currently being played.

Example code

This uses a loop to handle switching flag sets in the middle of a segment.

function handleFields() {
    while (readOffset < packetLength) {
        const fieldsetNum = readByte();
        const flags = readLong();
        
        if (fieldsetNum == 0) {
            if (flags & SQF_NAME) {
                const name = readString();
            }
            
            if (flags & SQF_URL) {
                const url = readString();
            }
            
            // ...
        }
        
        else if (fieldsetNum == 1) {
            if (flags & SQF2_PWAD_HASHES) {
                const numHashes = readByte();
                for (let i = 0; i < numHashes; i++) {
                    const hash = readString();
                }
            }
            
            // ...
        }
        
        if (!(flags & SQF_EXTENDED_INFO)) {
            break;
        }
    }
}

A variation that can be used with the old single-packet protocol:

function handleFields() {
    let fieldsetNum = 0;
    let flags = 0;
    
    while (readOffset < packetLength) {
        fieldsetNum = segmented ? readByte() : fieldsetNum;
        flags = readLong();
        
        if (fieldsetNum == 0) {
            // ...
        }
        
        else if (fieldsetNum == 1) {
            // ...
        }
        
        if (flags & SQF_EXTENDED_INFO) {
            fieldsetNum++;
        } else {
            break;
        }
    }
}