View source for Server queries

{{lang|Server Queries}}
You can query information from a running game server using UDP/IP packets. This document describes the packet formats and protocol to access this data.

= Data Types =

All server queries consist of five basic types of data packed together into a data stream. All types are little endian, which is the default on most languages on x86 CPUs.  Java users should use ByteBuffer to convert.

{| class=standard-table
! Name || Description
|-
| [[byte]] || 8 bit character or unsigned integer
|-
| [[short]] || 16 bit signed integer
|-
| [[long]] || 32 bit signed integer
|-
| [[float]] || 32 bit floating point
|-
| [[long]] [[long]] || 64 bit unsigned integer
|-
| [[string]] || variable-length byte field, encoded in UTF-8, terminated by 0x00
|}

= Protocol =

Steam uses a packet size of 1400 bytes + IP/UDP headers. If a request or response needs more packets for the data it starts the packets with an additional header.

== Simple Response Format ==

{| class=standard-table
! Data !! Type !! Comment
|-
| Header || [[long]] || Always equal to -1 (0xFFFFFFFF). Means it isn't split.
|-
| colspan="3" | Payload
|}

== Multi-packet Response Format ==

===[[Goldsource]] Server===

{| class=standard-table
! Data !! Type !! Comment
|-
| Header || [[long]] || Always equal to -2 (0xFFFFFFFE). Means the packet is split.
|-
| ID || [[long]] || Unique number assigned by server per answer.
|-
| Packet number || [[byte]] || Upper 4 bits represent the number of the current packet (starting at 0) and bottom 4 bits represent the total number of packets (2 to 15).
|-
| colspan="3" | Payload
|}

===[[Source]] Server===

{| class=standard-table
! Data !! Type !! Comment
|-
| Header || [[long]] || Always equal to -2 (0xFFFFFFFE). Means the packet is split.
|-
| ID || [[long]] || Same as the [[Goldsource]] server meaning. However, if the {{wiki|most significant bit}} is 1, then the response was compressed with bzip2 before being cut and sent. Refer to compression procedure below. 
|-
| Total || [[byte]] || The total number of packets in the response.
|-
| Number || [[byte]] || The number of the packet. Starts at 0.
|-
| Size || [[short]] || ([[Orange Box]] Engine and above only.) Maximum size of packet before packet switching occurs. The default value is 1248 bytes (0x04E0), but the server administrator can decrease this. For older engine versions: the maximum and minimum size of the packet was unchangeable. AppIDs which are known not to contain this field: 215, 17550, 17700, and 240 when protocol = 7.
|-
| colspan="3" | This is only present in the first packet of the response and only if the response is being compressed.
{| style="margin:10px"
! Data || Type || Comment
|-
| Size || [[long]] || Size of the whole response once it is decompressed.
|-
| CRC32 sum || [[long]] || CRC32 checksum of uncompressed response.
|}
To uncompress this response: collect and assemble all the payloads of the received packets, then pass that into a function like [http://www.bzip.org/1.0.3/html/util-fns.html#bzbufftobuffdecompress BZ2_bzBuffToBuffDecompress()] in C, [http://fr.php.net/manual/fr/function.bzdecompress.php bzdecompress()] in PHP, or [http://docs.python.org/2/library/bz2.html bz2.decompress()] in Python. Compression appears to have been phased out in newer Source games, but is still present in ~2006-era engines.
|-
| colspan="3" | Payload
|}

Because UDP packets can arrive in different order or delayed, every packet should be verified by its "ID" and "Number"! Every request or response with or without this header is continued with an integer -1 (0xFFFFFFFF) and the user data.
So by reading the first 4 bytes you can decide whether the data is split (-2) or in one packet (-1).

= Requests =

The server responds to 5 queries:

;<code>A2S_INFO</code>
:Basic information about the server.
;<code>A2S_PLAYER</code>
:Details about each player on the server.
;<code>A2S_RULES</code>
:The rules the server is using.
;<code>A2A_PING</code>
:Ping the server. (DEPRECATED)
;<code>A2S_SERVERQUERY_GETCHALLENGE</code>
:Returns a challenge number for use in the player and rules query. (DEPRECATED)

Queries should be sent in UDP packets to the listen port of the server.

== A2S_INFO ==

Retrieves information about the server including, but not limited to: its name, the map currently being played, and the number of players.

l4d2 server 2.2.1.3 update：some server will send challenge number ,it caused hlsw cant get server info;
=== Request Format ===

{| class=standard-table
! Data || Type || Value
|-
| Header || [[byte]] || 'T' (0x54)
|-
| Payload || [[string]] || "Source Engine Query\0"
|-
| Challenge || [[long]] || 4-byte challenge (sometimes -- see below)
|}

{|style="background:transparent;"
|
 FF FF FF FF 54 53 6F 75 72 63 65 20 45 6E 67 69   ÿÿÿÿTSource Engi
 6E 65 20 51 75 65 72 79 00                        ne Query.
|}

Example for challenge number:

Server response:
{|style="background:transparent;"
|
FF FF FF FF 41 0A 08 5E EA
|}
You need send :
{|style="background:transparent;"
|
FF FF FF FF 54 53 6F 75 72 63 65 20 45 6E 67 69 6E 65 20 51 75 65 72 79 00 0A 08 5E EA
|}


NOTE: In the future, additional data may be appended to the request!  Do not assume that if a request has extra data, that it is a bogus packet!

Servers may respond with the data immediately.  However, since this reply is larger than the request, it makes the server vulnerable to a reflection amplification attack.
Instead, the server may reply with a challenge to the client using S2C_CHALLENGE ('A' or 0x41).  In that case, the client should repeat the request by appending the challenge number.
This change was introduced in December 2020 to address the reflection attack vulnerability, and all clients are encouraged to support the new protocol.  See [https://steamcommunity.com/discussions/forum/14/2974028351344359625/ this post] for more info.

NOTE:changed 2021-6-19 13:05:43 :when l4d2 server received some packet from same ip address,it may deined replay


=== Response Format ===

{{Note|Both [[SiN 1 Multiplayer]] and [[Rag Doll Kung Fu]] utilise this response protocol.}}

{| class=standard-table
! Data !! Type !! Comment
|-
| Header || [[byte]] || Always equal to 'I' (0x49)
|-
| Protocol || [[byte]] || Protocol version used by the server.
|-
| Name || [[string]] || Name of the server.
|-
| Map || [[string]] || Map the server has currently loaded.
|-
| Folder || [[string]] || Name of the folder containing the game files.
|-
| Game || [[string]] || Full name of the game.
|-
| ID || [[short]] || [[Steam Application ID]] of game.
|-
| Players || [[byte]] || Number of players on the server.
|-
| Max. Players || [[byte]] || Maximum number of players the server reports it can hold.
|-
| Bots || [[byte]] || Number of bots on the server.
|-
| Server type || [[byte]] || Indicates the type of server: <ul><li>'d' for a dedicated server</li><li>'l' for a non-dedicated server</li><li>'p' for a [[SourceTV]] relay (proxy)</li></ul>
|-
| Environment || [[byte]] || Indicates the operating system of the server: <ul><li>'l' for Linux</li><li>'w' for Windows</li><li>'m' or 'o' for Mac (the code changed after L4D1)</li></ul>
|-
| Visibility || [[byte]] || Indicates whether the server requires a password: <ul><li>0 for public</li><li>1 for private</li></ul>
|-
| [[VAC]] || [[byte]] || Specifies whether the server uses VAC: <ul><li>0 for unsecured</li><li>1 for secured</li></ul>
|-
| colspan="3" | These fields only exist in a response if the server is running [[The Ship]]:
{| style="margin:10px;"
! Data || Type || Comment
|-
| Mode || [[byte]] || Indicates the game mode: <ul><li>0 for Hunt</li><li>1 for Elimination</li><li>2 for Duel</li><li>3 for Deathmatch</li><li>4 for VIP Team</li><li>5 for Team Elimination</li></ul>
|-
| Witnesses || [[byte]] || The number of witnesses necessary to have a player arrested.
|-
| Duration || [[byte]] || Time (in seconds) before a player is arrested while being witnessed. 
|}
|-
| Version || [[string]] || Version of the game installed on the server.
|-
| Extra Data Flag (EDF) || [[byte]] || If present, this specifies which additional data fields will be included.
|-
| colspan="3" | '''Only if''' <code>if ( EDF & 0x80 )</code> proves true:
{| style="margin:10px"
! Data || Type || Comment
|-
| Port || [[short]] || The server's game port number.
|}
|-
| colspan="3" | '''Only if''' <code>if ( EDF & 0x10 )</code> proves true:
{| style="margin:10px"
! Data || Type || Comment
|-
| [[SteamID]] || [[long]] long || Server's SteamID.
|}
|-
| colspan="3" | '''Only if''' <code>if ( EDF & 0x40 )</code> proves true:
{| style="margin:10px"
! Data || Type || Comment
|-
| Port || [[short]] || Spectator port number for [[SourceTV]].
|-
| Name || [[string]] || Name of the spectator server for SourceTV.
|}
|-
| colspan="3" | '''Only if''' <code>if ( EDF & 0x20 )</code> proves true:
{| style="margin:10px"
! Data || Type || Comment
|-
| Keywords || [[string]] || Tags that describe the game according to the server (for future use.)
|}
|-
| colspan="3" | '''Only if''' <code>if ( EDF & 0x01 )</code> proves true:
{| style="margin:10px"
! Data || Type || Comment
|-
| GameID || [[long]] long || The server's 64-bit GameID. If this is present, a more accurate AppID is present in the low 24 bits. The earlier AppID could have been truncated as it was forced into 16-bit storage.
|}
|}

{{Note|[[Rag Doll Kung Fu]] servers always return 0 for "Server type."}}

<br>

Example response for [[Counter-Strike: Source]]:
{|style="background:transparent;"
|
 FF FF FF FF 49 02 67 61 6D 65 32 78 73 2E 63 6F    ÿÿÿÿI.game2xs.co
 6D 20 43 6F 75 6E 74 65 72 2D 53 74 72 69 6B 65    m Counter-Strike
 20 53 6F 75 72 63 65 20 23 31 00 64 65 5F 64 75     Source #1.de_du
 73 74 00 63 73 74 72 69 6B 65 00 43 6F 75 6E 74    st.cstrike.Count
 65 72 2D 53 74 72 69 6B 65 3A 20 53 6F 75 72 63    er-Strike: Sourc
 65 00 F0 00 05 10 04 64 6C 00 00 31 2E 30 2E 30    e......dl..1.0.0
 2E 32 32 00                                        .22.
|}

Example response for [[The Ship]]:
{|style="background:transparent;"
|
 FF FF FF FF 49 07 53 68 69 70 20 53 65 72 76 65    ÿÿÿÿI.Ship Serve
 72 00 62 61 74 61 76 69 65 72 00 73 68 69 70 00    r.batavier.ship.
 54 68 65 20 53 68 69 70 00 60 09 01 05 00 6C 77    The Ship.`....lw
 00 00 01 03 03 31 2E 30 2E 30 2E 34 00             .....1.0.0.4.
|}

Example response for [[SiN 1 Multiplayer]]:
{|style="background:transparent;"
|
 FF FF FF FF 49 2F 53 65 6E 73 65 6D 61 6E 6E 20    ÿÿÿÿI/Sensemann 
 53 69 4E 20 44 4D 00 70 61 72 61 64 6F 78 00 53    SiN DM.paradox.S
 69 4E 20 31 00 53 69 4E 20 31 00 1D 05 00 10 00    iN 1.SiN 1......
 6C 77 00 00 31 2E 30 2E 30 2E 30 00                lw..1.0.0.0.
|}

Example response for [[Rag Doll Kung Fu]]:
{|style="background:transparent;"
|
 FF FF FF FF 49 FC 54 68 65 20 44 75 64 65 27 73     ÿÿÿÿIüThe Dude's
 20 64 6F 6A 6F 00 53 6F 63 63 65 72 00 52 44 4B      dojo.Soccer.RDK
 46 53 6F 63 63 65 72 00 52 61 67 44 6F 6C 6C 4B     FSoccer.RagDollK
 75 6E 67 46 75 3A 20 53 6F 63 63 65 72 00 EA 03     ungFu: Soccer.ê.
 01 04 00 00 77 00 00 32 2E 33 2E 30 2E 30 00        ....w..2.3.0.0.
|}


==== Obsolete [[GoldSource]] Response ====

GoldSource servers reply using the same response as Source servers. Older and pre-Steam servers still reply with the response format below. GoldSource can be distinguished from Source via AppIDs.

{| class=standard-table
! Data !! Type !! Comment
|-
| Header || [[byte]] || Always equal to 'm' (0x6D)
|-
| Address || [[string]] || IP address and port of the server.
|-
| Name || [[string]] || Name of the server.
|-
| Map || [[string]] || Map the server has currently loaded.
|-
| Folder || [[string]] || Name of the folder containing the game files.
|-
| Game || [[string]] || Full name of the game.
|-
| Players || [[byte]] || Number of players on the server.
|-
| Max. Players || [[byte]] || Maximum number of players the server reports it can hold.
|-
| Protocol || [[byte]] || Protocol version used by the server.
|-
| Server type || [[byte]] || Indicates the type of server: <ul><li>'D' for dedicated server</li><li>'L' for non-dedicated server</li><li>'P' for a HLTV server</li></ul>
|-
| Environment || [[byte]] || Indicates the operating system of the server: <ul><li>'L' for Linux</li><li>'W' for Windows</li></ul>
|-
| Visibility || [[byte]] || Indicates whether the server requires a password: <ul><li>0 for public</li><li>1 for private</li></ul>
|-
| Mod || [[byte]] || Indicates whether the game is a mod: <ul><li>0 for [[Half-Life]]</li><li>1 for Half-Life mod</li></ul>
|-
| colspan="3" | These fields are only present in the response if "Mod" is 1:
{| style="margin:10px"
! Data || Type || Comment
|-
| Link || [[string]] || URL to mod website.
|-
| Download Link || [[string]] || URL to download the mod.
|-
| NULL || [[byte]] || NULL byte (0x00)
|-
| Version || [[long]] || Version of mod installed on server.
|-
| Size || [[long]] || Space (in bytes) the mod takes up.
|-
| Type || [[byte]] || Indicates the type of mod: <ul><li>0 for single '''and''' multiplayer mod</li><li>1 for multiplayer '''only''' mod</li></ul>
|-
| DLL || [[byte]] || Indicates whether mod uses its own DLL: <ul><li>0 if it uses the [[Half-Life]] DLL</li><li>1 if it uses its own DLL</li></ul>
|}
|-
| [[VAC]] || [[byte]] || Specifies whether the server uses VAC: <ul><li>0 for unsecured</li><li>1 for secured</li></ul>
|-
| Bots || [[byte]] || Number of bots on the server.
|}

{{Note|HLTV servers may respond with a late request that is either incomplete or incorrect if the number of slots is 255.}}

<br>

Example response:
{| style="background:transparent;"
|
 FF FF FF FF 6D 37 37 2E 31 31 31 2E 31 39 34 2E    ÿÿÿÿm77.111.194.
 31 31 30 3A 32 37 30 31 35 00 46 52 20 2D 20 56    110:27015.FR - V
 65 72 79 47 61 6D 65 73 2E 6E 65 74 20 2D 20 44    eryGames.net - D
 65 61 74 6D 61 74 63 68 20 2D 20 6F 6E 6C 79 20    eatmatch - only 
 73 75 72 66 5F 73 6B 69 20 2D 20 6E 67 52 00 73    surf_ski - ngR.s
 75 72 66 5F 73 6B 69 00 63 73 74 72 69 6B 65 00    urf_ski.cstrike.
 43 6F 75 6E 74 65 72 2D 53 74 72 69 6B 65 00 0C    Counter-Strike..
 12 2F 64 6C 00 01 77 77 77 2E 63 6F 75 6E 74 65    ./dl..www.counte
 72 2D 73 74 72 69 6B 65 2E 6E 65 74 00 00 00 01    r-strike.net....
 00 00 00 00 9E F7 0A 00 01 01 00                   ....ž÷.....
|}

== A2S_PLAYER ==

This query retrieves information about the players currently on the server. It needs an initial step to acquire a challenge number.

{{Note|[[SourceTV]] does not respond to this request.}}

=== Request Format ===

{| class=standard-table
! Data || Type || Value
|-
| Header || [[byte]] || 'U' (0x55)
|-
| Challenge || [[int]] || Challenge number, or -1 (0xFFFFFFFF) to receive a challenge number.
|}

Challenge response format:
{| class=standard-table
! Data || Type || Value
|-
| Header || [[byte]] || 'A' (0x41)
|-
| Challenge || [[int]] || Challenge number.
|}

Example challenge request:
{| style="background:transparent;"
|
 FF FF FF FF 55 FF FF FF FF                         ÿÿÿÿUÿÿÿÿ"       
|}

Example challenge response:
{| style="background:transparent;"
|
 FF FF FF FF 41 4B A1 D5 22                         ÿÿÿÿAÿÿÿÿ"       
|}

Example A2S_PLAYER request with the received challenge number:
{| style="background:transparent;"
|
 FF FF FF FF 55 4B A1 D5 22                         ÿÿÿÿUÿÿÿÿ"       
|}

=== Response Format ===

{| class=standard-table
! Data !! Type !! Comment
|-
| Header || [[byte]] || Always equal to 'D' (0x44)
|-
| Players || [[byte]] || Number of players whose information was gathered.
|-
| colspan="3" | For every player in "Players" there is this chunk in the response:
{| style="margin:10px"
! Data || Type || Comment
|-
| Index || [[byte]] || Index of player chunk starting from 0.
|-
| Name || [[string]] || Name of the player.
|-
| Score || [[long]] || Player's score (usually "frags" or "kills".)
|-
| Duration || [[float]] || Time (in seconds) player has been connected to the server.
|}
|}

[[The Ship]] additional player info (comes after the basic information in the packet):

{| class=standard-table
! Data || Type || Comment
|-
| Deaths || [[long]] || Player's deaths 
|-
| Money || [[long]] || Player's money
|}

{{Note|When a player is trying to connect to a server, they are recorded in the number of players. However, they will not be in the list of player information chunks.}}

{{Warning|CS:GO Server by default returns only max players and server uptime. You have to change server cvar "host_players_show" in server.cfg to value "2" if you want to revert to old format with players list.}}


<br>

Example response:
{| style="background:transparent;"
|
 FF FF FF FF 44 02 01 5B 44 5D 2D 2D 2D 2D 3E 54    ÿÿÿÿD..[D]---->T
 2E 4E 2E 57 3C 2D 2D 2D 2D 00 0E 00 00 00 B4 97    .N.W<----.....´—
 00 44 02 4B 69 6C 6C 65 72 20 21 21 21 00 05 00    .D.Killer !!!...
 00 00 69 24 D9 43                                  ..i$ÙC
|}

[[The Ship]] response:
{| style="background:transparent;"
|
 FF FF FF FF 44 13 00 53 68 69 70 6D 61 74 65 31    ▒▒▒▒D..Shipmate1
 00 00 00 00 00 00 00 80 BF 01 53 68 69 70 6D 61    .......▒▒.Shipma
 74 65 32 00 00 00 00 00 00 00 80 BF 02 53 68 69    te2.......▒▒.Shi
 70 6D 61 74 65 33 00 00 00 00 00 00 00 80 BF 03    pmate3.......▒▒.
 53 68 69 70 6D 61 74 65 34 00 00 00 00 00 00 00    Shipmate4.......
 80 BF 04 53 68 69 70 6D 61 74 65 35 00 00 00 00    ▒▒.Shipmate5....
 00 00 00 80 BF 07 28 31 29 4C 61 6E 64 4C 75 62    ...▒▒.(1)LandLub
 62 65 72 00 00 00 00 00 D3 8E 68 45 00 00 00 00    ber.....ӎhE....
 C4 09 00 00 00 00 00 00 C4 09 00 00 00 00 00 00    ▒.......▒.......
 C4 09 00 00 00 00 00 00 C4 09 00 00 00 00 00 00    ▒.......▒.......
 C4 09 00 00 00 00 00 00 C4 09 00 00                ▒.......▒...    
|}

== A2S_RULES ==

Returns the server rules, or configuration variables in name/value pairs. This query requires an initial challenge step.

The [[Console variable]]s included are the ones marked with [[FCVAR_NOTIFY]] as well as any additional ones listed in the server configuration.

=== Request Format ===

{| class=standard-table
! Data || Type || Value
|-
| Header || [[byte]] || 'V' (0x56)
|-
| Challenge || [[long]] || Challenge number, or -1 (0xFFFFFFFF) to receive a challenge number.
|}

Challenge response format:
{| class=standard-table
! Data || Type || Value
|-
| Header || [[byte]] || 'A' (0x41)
|-
| Challenge || [[long]] || Challenge number.
|}

Example challenge request:
{| style="background:transparent;"
|
 FF FF FF FF 56 FF FF FF FF                         ÿÿÿÿVÿÿÿÿ"       
|}

Example challenge response:
{| style="background:transparent;"
|
 FF FF FF FF 41 4B A1 D5 22                         ÿÿÿÿVK¡Õ"       
|}

{{Warning|Some servers will bypass replying with a challenge, and instead will immediately send a full rules response. This has been observed in a few servers that have modified their network code and in servers running older engines. A simple way to detect this situation is if the packet header is -2 (0xFFFFFFFE), or -1 (0xFFFFFFFF) with a message header of 0x45 ('E').}}

{{Warning|CS:GO Rules reply is broken since update CSGO 1.32.3.0 (Feb 21, 2014). Before the update rules got truncated when exceeding MTU, after the update rules reply is not sent at all. You can also see a console message: [NET] Cannot send connectionless packet to xxx.xxx.xxx.xxx:xxxxx '0x45' exceeding MTU (2644)}}

Final request that includes the received challenge number:
{| style="background:transparent;"
|
 FF FF FF FF 56 4B A1 D5 22                         ÿÿÿÿVK¡Õ"       
|}

=== Response Format ===

{{Note|Responses to this query are usually multi-packeted.}}

{| class=standard-table
! Data !! Type !! Comment
|-
| Header || [[byte]] || Always equal to 'E' (0x45)
|-
| Rules || [[short]] || Number of rules in the response.
|-
| colspan="3" | For every rule in "Rules" there is this chunk in the response:
{| style="margin:10px;"
! Data || Type || Comment
|-
| Name || [[string]] || Name of the rule.
|-
| Value || [[string]] || Value of the rule.
|}
|}

{{Warning|Older games, usually on Source SDK 2007, may reply with a truncated single packet reply. In this case, the message may be terminated in the middle of a string or in between a name and value.}}

Example response:

{| style="background:transparent;"
|
 <span style="color:blue">FE FF FF FF 56 0A 00 00 02</span> FF FF FF FF 45 5D 00    þÿÿÿV....ÿÿÿÿE].
 5F 74 75 74 6F 72 5F 62 6F 6D 62 5F 76 69 65 77    _tutor_bomb_view
 61 62 6C 65 5F 63 68 65 63 6B 5F 69 6E 74 65 72    able_check_inter
 76 61 6C 00 30 2E 35 00 5F 74 75 74 6F 72 5F 64    val.0.5._tutor_d
 65 62 75 67 5F 6C 65 76 65 6C 00 30 00 5F 74 75    ebug_level.0._tu
 74 6F 72 5F 65 78 61 6D 69 6E 65 5F 74 69 6D 65    tor_examine_time
 00 30 2E 35 00 5F 74 75 74 6F 72 5F 68 69 6E 74    .0.5._tutor_hint
 5F 69 6E 74 65 72 76 61 6C 5F 74 69 6D 65 00 31    _interval_time.1
 30 2E 30 00 5F 74 75 74 6F 72 5F 6C 6F 6F 6B 5F    0.0._tutor_look_
 61 6E 67 6C 65 00 31 30 00 5F 74 75 74 6F 72 5F    angle.10._tutor_
 6C 6F 6F 6B 5F 64 69 73 74 61 6E 63 65 00 32 30    look_distance.20
 30 00 5F 74 75 74 6F 72 5F 6D 65 73 73 61 67 65    0._tutor_message
 5F 63 68 61 72 61 63 74 65 72 5F 64 69 73 70 6C    _character_displ
 61 79 5F 74 69 6D 65 5F 63 6F 65 66 66 69 63 69    ay_time_coeffici
 65 6E 74 00 30 2E 30 37 00 5F 74 75 74 6F 72 5F    ent.0.07._tutor_
 6D 65 73 73 61 67 65 5F 6D 69 6E 69 6D 75 6D 5F    message_minimum_
 64 69 73 70 6C 61 79 5F 74 69 6D 65 00 31 00 5F    display_time.1._
 74 75 74 6F 72 5F 6D 65 73 73 61 67 65 5F 72 65    tutor_message_re
 70 65 61 74 73 00 35 00 5F 74 75 74 6F 72 5F 76    peats.5._tutor_v
 69 65 77 5F 64 69 73 74 61 6E 63 65 00 31 30 30    iew_distance.100
 30 00 61 6C 6C 6F 77 5F 73 70 65 63 74 61 74 6F    0.allow_spectato
 72 73 00 31 00 61 6D 78 5F 63 6C 69 65 6E 74 5F    rs.1.amx_client_
 6C 61 6E 67 75 61 67 65 73 00 31 00 61 6D 78 5F    languages.1.amx_
 6C 61 6E 67 75 61 67 65 00 66 72 00 61 6D 78 5F    language.fr.amx_
 6E 65 78 74 6D 61 70 00 64 65 5F 61 7A 74 65 63    nextmap.de_aztec
 00 61 6D 78 5F 74 69 6D 65 6C 65 66 74 00 30 30    .amx_timeleft.00
 3A 30 30 00 61 6D 78 6D 6F 64 78 5F 76 65 72 73    :00.amxmodx_vers
 69 6F 6E 00 31 2E 37 36 64 00 63 6F 6F 70 00 30    ion.1.76d.coop.0
 00 63 73 64 6D 5F 61 63 74 69 76 65 00 31 00 63    .csdm_active.1.c
 73 64 6D 5F 76 65 72 73 69 6F 6E 00 32 2E 31 00    sdm_version.2.1.
 64 65 61 74 68 6D 61 74 63 68 00 31 00 64 65 63    deathmatch.1.dec
 61 6C 66 72 65 71 75 65 6E 63 79 00 36 30 00 65    alfrequency.60.e
 64 67 65 66 72 69 63 74 69 6F 6E 00 32 00 68 6F    dgefriction.2.ho
 73 74 61 67 65 5F 64 65 62 75 67 00 30 00 68 6F    stage_debug.0.ho
 73 74 61 67 65 5F 73 74 6F 70 00 30 00 68 75 6D    stage_stop.0.hum
 61 6E 73 5F 6A 6F 69 6E 5F 74 65 61 6D 00 61 6E    ans_join_team.an
 79 00 6A 74 70 31 30 31 38 31 00 63 68 75 74 65    y.jtp10181.chute
 00 6D 61 78 5F 71 75 65 72 69 65 73 5F 73 65 63    .max_queries_sec
 00 31 00 6D 61 78 5F 71 75 65 72 69 65 73 5F 73    .1.max_queries_s
 65 63 5F 67 6C 6F 62 61 6C 00 31 00 6D 61 78 5F    ec_global.1.max_
 71 75 65 72 69 65 73 5F 77 69 6E 64 6F 77 00 31    queries_window.1
 00 6D 65 74 61 6D 6F 64 5F 76 65 72 73 69 6F 6E    .metamod_version
 00 31 2E 31 39 00 6D 70 5F 61 6C 6C 6F 77 6D 6F    .1.19.mp_allowmo
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 73 74 65 6E 63 79 00 31 00 6D 70 5F 66 61 64 65    stency.1.mp_fade
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 65 63 61 6D 65 72 61 00 30 00 6D 70 5F 66 6F 72    ecamera.0.mp_for
 63 65 63 68 61 73 65 63 61 6D 00 30 00 6D 70 5F    cechasecam.0.mp_
 66 72 61 67 73 6C 65 66 74 00 30 00 6D 70 5F 66    fragsleft.0.mp_f
 72 65 65 66 6F 72 61 6C 6C 00 30 00 6D 70 5F 66    reeforall.0.mp_f
 72 65 65 7A 65 74 69 6D 65 00 32 00 6D 70 5F 66    reezetime.2.mp_f
 72 69 65 6E 64 6C 79 66 69 72 65 00 30 00 6D 70    riendlyfire.0.mp
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 30 2E 31 00 6D 70 5F 68 6F 73 74 61 67 65 70 65    0.1.mp_hostagepe
 6E 61 6C 74 79 00 31 33 00 6D 70 5F 6B 69 63 6B    nalty.13.mp_kick
 70 65 72 63 65 6E 74 00 30 00 6D 70 5F 6C 69 6D    percent.0.mp_lim
 69 74 74 65 61 6D 73 00 30 00 6D 70 5F 6C 6F 67    itteams.0.mp_log
 64 65 74 61 69 6C 00 33 00 6D 70 5F 6C 6F 67 66    detail.3.mp_logf
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 61 67 65 73 00 31 00 6D 70 5F 6D 61 70 76 6F 74    ages.1.mp_mapvot
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 73 76 5F 61 69 6D 00 30 00 73 76 5F 61 69 72 61    sv_aim.0.sv_aira
 63 63 65 6C 65 72 61 74 65 00 31 30 30 00 73 76    ccelerate.100.sv
 5F 61 69 72 6D 6F 76 65 00 31 00 73 76 5F 61 6C    _airmove.1.sv_al
 6C 6F 77 75 70 6C 6F 61 64 00 31 00 73 76 5F 61    lowupload.1.sv_a
 6C 6C 74 61 6C 6B 00 31 00 73 76 5F 62 6F 75 6E    lltalk.1.sv_boun
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 31 00 73 76 5F 63 6C 69 70 6D 6F 64 65 00 30 00    1.sv_clipmode.0.
 73 76 5F 63 6F 6E 74 61                            sv_conta

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 61 76 69 74 79 00 37 35 30 00 73 76 5F 6C 6F 67    avity.750.sv_log
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 73 70 65 65 64 00 33 32 30 00 73 76 5F 6D 69 6E    speed.320.sv_min
 72 61 74 65 00 31 35 30 30 30 00 73 76 5F 70 61    rate.15000.sv_pa
 73 73 77 6F 72 64 00 30 00 73 76 5F 70 72 6F 78    ssword.0.sv_prox
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 00 73 76 5F 73 74 65 70 73 69 7A 65 00 31 38 00    .sv_stepsize.18.
 73 76 5F 73 74 6F 70 73 70 65 65 64 00 37 35 00    sv_stopspeed.75.
 73 76 5F 75 70 6C 6F 61 64 6D 61 78 00 30 2E 35    sv_uploadmax.0.5
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 31 00 73 76 5F 77 61 74 65 72 61 63 63 65 6C 65    1.sv_wateraccele
 72 61 74 65 00 31 30 00 73 76 5F 77 61 74 65 72    rate.10.sv_water
 66 72 69 63 74 69 6F 6E 00 31 00                   friction.1.
|}

== A2A_PING ==

Ping the server to see if it exists, this can be used to calculate the latency to the server.

{{Warning|According to Valve (see [[Talk:Server_queries#A2A_PING_no_longer_supported.3F|Talk Page]]), A2A_PING is no longer supported on Counter-Strike: Source and Team Fortress 2 servers, and is considered a deprecated feature.}}

=== Request Format ===

{| class=standard-table
! Data || Type || Value
|-
| Header || [[byte]] || 'i' (0x69)
|}

{| style="background:transparent;"
|
 FF FF FF FF 69                                     ÿÿÿÿi           
|}

=== Response Format ===

==== [[Goldsource]] Server ====

{| class=standard-table
! Data || Type || Value
|-
| Header || [[byte]] || 'j' (0x6A)
|-
| Payload || [[string]] || Null
|}

{| style="background:transparent;"
|
 FF FF FF FF 6A 00                                  ÿÿÿÿj.           
|}

==== [[Source]] Server ====

{| class=standard-table
! Data || Type || Value
|-
| Heading || [[byte]] || 'j' (0x6A)
|-
| Payload || [[string]] || '00000000000000.'
|}

{| style="background:transparent;"
|
 FF FF FF FF 6A 30 30 30 30 30 30 30 30 30 30 30    ÿÿÿÿj00000000000
 30 30 30 00                                        000.
|}

== A2S_SERVERQUERY_GETCHALLENGE ==

A2S_PLAYER and A2S_RULES queries both require a challenge number. Formerly, this number could be obtained via an A2S_SERVERQUERY_GETCHALLENGE request. In newer games it no longer works. Instead, issue A2S_PLAYER or A2S_RULES queries with an initial challenge of <code>-1 (0xFFFFFFFF)</code> to receive a usable challenge number.

On some engines (confirmed AppIDs: 17510, 17530, 17740, 17550, 17700) it can be used. The format is:

=== Request Format ===

{| class=standard-table
! Data || Type || Value
|-
| Header || [[byte]] || 'W' (0x57)
|}

{| style="background:transparent;"
|
 FF FF FF FF 57                                     ÿÿÿÿW           
|}

=== Response Format ===

{| class=standard-table
! Data || Type || Comment
|-
| Header || [[byte]] || Should be equal to 'A' (0x41.)
|-
| Challenge || [[long]] || The challenge number to use.
|}

Example response:

{| style="background:transparent;"
|
 FF FF FF FF 41 4B A1 D5 22                         ÿÿÿÿAK¡Õ"       
|}

= Implementations =

* [https://www.npmjs.com/package/@fabricio-191/valve-server-query @fabricio-191/valve-server-query] Server, Master Server and RCON protocols implementation for Node.js
* [https://www.npmjs.com/package/steam-server-query Steam Server Query] Javascript (Node.js) module which implements the Master Server Query Protocol and Game Server Queries
* [https://github.com/ribasco/async-gamequery-lib Asynchronous Game Query Library] A Java 8 based Asynchronous Game Query Library powered by Netty
* [[Source Server Query Library]] C library
* [https://github.com/BinaryAlien/libssq libssq] C library
* [http://www.barkerjr.net/gameserver.html GameServer] Java library
* [http://queried.sourceforge.net QueryEd] Java library
* [[Steam Condenser]] Java, PHP, and Ruby library
* [https://github.com/sonicsnes/node-gamedig GameDig] Javascript (Node.JS) module
* [http://search.cpan.org/~masanorih/ Net-SRCDS-Queries] Perl module
* [https://github.com/TronPaul/srcdspy SRCDSpy] Python library
* [http://github.com/frostschutz/SourceLib SourceLib] Python library
* [http://github.com/Holiverh/python-valve python-valve] Python library
* [https://pypi.python.org/pypi/valve-range-query/1.0.4 valve-range-query] Python Library for IP range query
* [https://github.com/Yepoleb/python-a2s python-a2s] Python library (supports async)
* [https://github.com/Yepoleb/dayzquery dayzquery] Add-on for [https://github.com/Yepoleb/python-a2s python-a2s] library which parses DayZ-specific binary data in A2S_RULES response 
* [http://www.codeproject.com/KB/game/Game_Server_Query_DLL.aspx aQuery] VB.NET library
* [https://github.com/atomy/sourcestats/ SourceStats] Source Server Statistics
* [https://github.com/xPaw/PHP-Source-Query-Class PHP Source Query] PHP library
* [http://querymaster.codeplex.com/ QueryMaster] C# library
* [https://github.com/armageddonapps/QueryMaster QueryMaster] C# library (remaster for .NET Standart 2.0)
* [https://github.com/Florian2406/Okolni-Source-Query Okolni-Source-Query] C# library (.NET Standard 2.0, Now Support l4d2 2213)
* [https://github.com/Crytilis/A2S A2S] C# library utilizing NET5. (Currently supports A2S_Info and A2S_Player)
* [https://github.com/rumblefrog/go-a2s/ go-a2s] Golang library
* [https://github.com/rumblefrog/a2s-rs/ a2s-rs] Rust library
* [https://github.com/hundunzhidian/RconA2sAPi Rcon and A2s WebApi]中文的WebApi协议库,基于Spring boot,仅支持A2S_INFO、A2S_PLAYER,Now Support l4d2 2213
* [https://github.com/hjorslev/SteamPS SteamPS] Module that utilizes PowerShell as a wrapper for SteamCMD. Uses server queries in the command [https://github.com/hjorslev/SteamPS/blob/master/SteamPS/Public/Get-SteamServerInfo.ps1 Get-SteamServerInfo]
* [https://github.com/hundunzhidian/valvemiraibot Mirai Tencent QQ robot]基于mriaiBot适配了a2s rcon的腾讯qq机器人,仅支持A2S_INFO、A2S_PLAYER,Rcon,Now Support l4d2 2213
* [https://github.com/gamedig/rust-gamedig/ Rust-GameDig] Rust library that supports the entirety of the protocol (also has the obsolete GoldSrc response).

= See Also =

* [[Master Server Query Protocol]]
* [[Source RCON Protocol]]

[[Category:Networking]]
[[Category:Technical]]
[[Category:Dedicated Server]]