Server queries: Difference between revisions

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m (update A2S_PLAYERS to not use SERVERQUERY_CHALLENGE)
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{{otherlang2
{{LanguageBar}}
|fr = Server_Queries:fr
}}


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.
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 =
== 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.
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.
Line 25: Line 23:
|}
|}


= Protocol =
== 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.
Steam uses a packet size of up to 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 ==
2023-07-10: Rust has been observed breaking this, sending packets up to the maximum IP size (64KB).
 
=== Simple Response Format ===


{| class=standard-table
{| class=standard-table
Line 39: Line 39:
|}
|}


== Multi-packet Response Format ==
=== Multi-packet Response Format ===


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


{| class=standard-table
{| class=standard-table
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|}
|}


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


{| class=standard-table
{| class=standard-table
Line 62: Line 62:
| Header || [[long]] || Always equal to -2 (0xFFFFFFFE). Means the packet is split.
| 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.  
| 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.
| Total || [[byte]] || The total number of packets in the response.
Line 68: Line 68:
| Number || [[byte]] || The number of the packet. Starts at 0.
| 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.
| 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.
| colspan="3" | This is only present in the first packet of the response and only if the response is being compressed.
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So by reading the first 4 bytes you can decide whether the data is split (-2) or in one packet (-1).
So by reading the first 4 bytes you can decide whether the data is split (-2) or in one packet (-1).


= Requests =
Note: Some titles when using the split packet method have been observed erroneously nesting the single message header inside the split payload.
 
== Requests ==


The server responds to 5 queries:
The server responds to 5 queries:
Line 103: Line 105:
Queries should be sent in UDP packets to the listen port of the server.
Queries should be sent in UDP packets to the listen port of the server.


== A2S_INFO ==
== Challenge Mechanism ==
 
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.
 
Previously the structure of this document made it seem that only A2S_INFO messages would be responded with in this manner, however ANY of the queries made MAY result in a `S2C_CHALLENGE` response if either the challenge was omitted, is wrong, or has expired.
 
=== A2S_INFO ===


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


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


Line 120: Line 133:
|
|
  FF FF FF FF 54 53 6F 75 72 63 65 20 45 6E 67 69  ÿÿÿÿTSource Engi
  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
  6E 65 20 51 75 65 72 79 00                        ne Query.
|}
|}


=== Response Format ===
Example for challenge number:


==== [[Goldsource]] Server ====
Server response:
 
{|style="background:transparent;"
{{Warning|This is obsolete.  GoldSource servers (except for HLTV ones?) now report using the same protocol as Source servers.  To differentiate between (for example) Counter-Strike and Counter-Strike: Source, or other games with the same gamedir, use the Steam AppId.}}
|
 
FF FF FF FF 41 0A 08 5E EA
{| 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>
|}
|}
|-
You need send :
| [[VAC]] || [[byte]] || Specifies whether the server uses VAC: <ul><li>0 for unsecured</li><li>1 for secured</li></ul>
{|style="background:transparent;"
|-
|
| Bots || [[byte]] || Number of bots on the server.
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|HLTV servers may respond with a late request that is either incomplete or incorrect if the number of slots is 255.}}


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


Example response:
NOTE:some older titles have been observed sending the GoldSource INFO packet AND the newer INFO packet in reply to this.
{| 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÷.....
|}


==== [[Source]] Server ====
==== Response Format ====


{{Note|Both [[SiN 1 Multiplayer]] and [[Rag Doll Kung Fu]] utilise this response protocol.}}
{{Note|Both [[SiN 1 Multiplayer]] and [[Rag Doll Kung Fu]] utilise this response protocol.}}
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! Data !! Type !! Comment
! Data !! Type !! Comment
|-
|-
| Header || [[byte]] || Always equal to 'I' (0x49.)
| Header || [[byte]] || Always equal to 'I' (0x49)
|-
|-
| Protocol || [[byte]] || Protocol version used by the server.
| Protocol || [[byte]] || Protocol version used by the server.
Line 228: Line 183:
| Bots || [[byte]] || Number of bots on the server.
| 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]] server</li></ul>
| 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>
| 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>
Line 293: Line 248:
<br>
<br>


Example response for [[Counter Strike: Source]]:
Example response for [[Counter-Strike: Source]]:
{|style="background:transparent;"
{|style="background:transparent;"
|
|
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|}
|}


== A2S_PLAYER ==
 
===== 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.
This query retrieves information about the players currently on the server. It needs an initial step to acquire a challenge number.
Line 339: Line 371:
{{Note|[[SourceTV]] does not respond to this request.}}
{{Note|[[SourceTV]] does not respond to this request.}}


=== Request Format ===
==== Request Format ====


{| class=standard-table
{| class=standard-table
Line 346: Line 378:
| Header || [[byte]] || 'U' (0x55)
| Header || [[byte]] || 'U' (0x55)
|-
|-
| Challenge || [[long]] || -1 (0xFFFFFFFF) to receive a challenge number.
| 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.
|}
|}


Line 358: Line 399:
{| style="background:transparent;"
{| style="background:transparent;"
|
|
  FF FF FF FF 41 4B A1 D5 22                        ÿÿÿÿUÿÿÿÿ"       
  FF FF FF FF 41 4B A1 D5 22                        ÿÿÿÿAÿÿÿÿ"       
|}
|}


Line 367: Line 408:
|}
|}


=== Response Format ===
==== Response Format ====


{| class=standard-table
{| class=standard-table
! Data !! Type !! Comment
! Data !! Type !! Comment
|-
|-
| Header || [[byte]] || Always equal to 'D' (0x44.)
| Header || [[byte]] || Always equal to 'D' (0x44)
|-
|-
| Players || [[byte]] || Number of players whose information was gathered.
| Players || [[byte]] || Number of players whose information was gathered.
Line 388: Line 429:
| Duration || [[float]] || Time (in seconds) player has been connected to the server.
| 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.}}
{{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>
<br>
Line 403: Line 457:
|}
|}


== A2S_RULES ==
[[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.
Returns the server rules, or configuration variables in name/value pairs. This query requires an initial challenge step.


=== Request Format ===
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
{| class=standard-table
Line 414: Line 486:
| Header || [[byte]] || 'V' (0x56)
| Header || [[byte]] || 'V' (0x56)
|-
|-
| Challenge || [[long]] || Challenge number retrieved via <code>A2S_SERVERQUERY_GETCHALLENGE</code> or -1 to get challenge number.
| 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"     
|}
|}


Line 423: Line 510:
|}
|}


{{Warning|Some servers will bypass sending a rules challenge and immediately reply with a 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 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:
Final request that includes the received challenge number:
Line 431: Line 518:
|}
|}


=== Response Format ===
==== Response Format ====


{{Note|Responses to this query are usually multi-packeted.}}
{{Note|Responses to this query are usually multi-packeted.}}
Line 438: Line 525:
! Data !! Type !! Comment
! Data !! Type !! Comment
|-
|-
| Header || [[byte]] || Always equal to 'E' (0x45.)
| Header || [[byte]] || Always equal to 'E' (0x45)
|-
|-
| Rules || [[short]] || Number of rules in the response.
| Rules || [[short]] || Number of rules in the response.
Line 452: Line 539:
|}
|}


{{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.}}
=== A2A_PING ===
 
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
6E 73 74 65 72 73 00 30 00 6D 70 5F 61 75 74 6F    nsters.0.mp_auto
6B 69 63 6B 00 30 00 6D 70 5F 61 75 74 6F 74 65    kick.0.mp_autote
61 6D 62 61 6C 61 6E 63 65 00 30 00 6D 70 5F 62    ambalance.0.mp_b
75 79 74 69 6D 65 00 39 39 39 39 00 6D 70 5F 63    uytime.9999.mp_c
34 74 69 6D 65 72 00 33 35 00 6D 70 5F 63 68 61    4timer.35.mp_cha
74 74 69 6D 65 00 35 00 6D 70 5F 63 6F 6E 73 69    ttime.5.mp_consi
73 74 65 6E 63 79 00 31 00 6D 70 5F 66 61 64 65    stency.1.mp_fade
74 6F 62 6C 61 63 6B 00 30 00 6D 70 5F 66 6C 61    toblack.0.mp_fla
73 68 6C 69 67 68 74 00 31 00 6D 70 5F 66 6F 6F    shlight.1.mp_foo
74 73 74 65 70 73 00 31 00 6D 70 5F 66 6F 72 63    tsteps.1.mp_forc
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
5F 67 68 6F 73 74 66 72 65 71 75 65 6E 63 79 00    _ghostfrequency.
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
69 6C 65 00 31 00 6D 70 5F 6C 6F 67 6D 65 73 73    ile.1.mp_logmess
61 67 65 73 00 31 00 6D 70 5F 6D 61 70 76 6F 74    ages.1.mp_mapvot
65 72 61 74 69 6F 00 31 00 6D 70 5F 6D 61 78 72    eratio.1.mp_maxr
6F 75 6E 64 73 00 30 00 6D 70 5F 6D 69 72 72 6F    ounds.0.mp_mirro
72 64 61 6D 61 67 65 00 30 00 6D 70 5F 70 6C 61    rdamage.0.mp_pla
79 65 72 69 64 00 30 00 6D 70 5F 72 6F 75 6E 64    yerid.0.mp_round
74 69 6D 65 00 33 00 6D 70 5F 73 74 61 72 74 6D    time.3.mp_startm
6F 6E 65 79 00 38 30 30 00 6D 70 5F 74 69 6D 65    oney.800.mp_time
6C 65 66 74 00 30 00 6D 70 5F 74 69 6D 65 6C 69    left.0.mp_timeli
6D 69 74 00 30 00 6D 70 5F 74 6B 70 75 6E 69 73    mit.0.mp_tkpunis
68 00 30 00 6D 70 5F 77 69 6E 64 69 66 66 65 72    h.0.mp_windiffer
65 6E 63 65 00 31 00 6D 70 5F 77 69 6E 6C 69 6D    ence.1.mp_winlim
69 74 00 30 00 70 61 75 73 61 62 6C 65 00 31 00    it.0.pausable.1.
73 76 5F 61 63 63 65 6C 65 72 61 74 65 00 35 00    sv_accelerate.5.
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
63 65 00 31 00 73 76 5F 63 68 65 61 74 73 00 30    ce.1.sv_cheats.0
00 73 76 5F 63 6C 69 65 6E 74 74 72 61 63 65 00    .sv_clienttrace.
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
 
<span style="color:blue">FE FF FF FF 56 0A 00 00 12</span> 63 74 00 00 73 76 5F    þÿÿÿV....ct..sv_
66 72 69 63 74 69 6F 6E 00 34 00 73 76 5F 67 72    friction.4.sv_gr
61 76 69 74 79 00 37 35 30 00 73 76 5F 6C 6F 67    avity.750.sv_log
62 6C 6F 63 6B 73 00 30 00 73 76 5F 6D 61 78 72    blocks.0.sv_maxr
61 74 65 00 32 35 30 30 30 00 73 76 5F 6D 61 78    ate.25000.sv_max
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
69 65 73 00 32 00 73 76 5F 72 65 67 69 6F 6E 00    ies.2.sv_region.
33 00 73 76 5F 72 65 73 74 61 72 74 00 30 00 73    3.sv_restart.0.s
76 5F 72 65 73 74 61 72 74 72 6F 75 6E 64 00 30    v_restartround.0
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
00 73 76 5F 76 6F 69 63 65 65 6E 61 62 6C 65 00    .sv_voiceenable.
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.
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.}}
{{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 ===
==== Request Format ====


{| class=standard-table
{| class=standard-table
Line 586: Line 558:
|}
|}


=== Response Format ===
==== Response Format ====


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


{| class=standard-table
{| class=standard-table
Line 603: Line 575:
|}
|}


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


{| class=standard-table
{| class=standard-table
Line 610: Line 582:
| Heading || [[byte]] || 'j' (0x6A)
| Heading || [[byte]] || 'j' (0x6A)
|-
|-
| Payload || [[string]] || '00000000000000'
| Payload || [[string]] || '00000000000000.'
|}
|}


Line 619: Line 591:
|}
|}


== A2S_SERVERQUERY_GETCHALLENGE ==
=== 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.
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.
Line 625: Line 597:
On some engines (confirmed AppIDs: 17510, 17530, 17740, 17550, 17700) it can be used. The format is:
On some engines (confirmed AppIDs: 17510, 17530, 17740, 17550, 17700) it can be used. The format is:


=== Request Format ===
==== Request Format ====


{| class=standard-table
{| class=standard-table
Line 638: Line 610:
|}
|}


=== Response Format ===
==== Response Format ====


{| class=standard-table
{| class=standard-table
Line 655: Line 627:
|}
|}


= Implementations =
== 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
* [[Source Server Query Library]] C library
* [https://github.com/BinaryAlien/libssq libssq] C library
* [http://www.barkerjr.net/gameserver.html GameServer] Java library
* [http://www.barkerjr.net/gameserver.html GameServer] Java library
* [http://queried.sourceforge.net QueryEd] Java library
* [http://queried.sourceforge.net QueryEd] Java library
* [[Steam Condenser]] Java, PHP, and Ruby library
* [[Steam Condenser]] Java, PHP, and Ruby library
* [http://search.cpan.org/~masanorih/Net-SRCDS-Queries-0.0.3/ Net-SRCDS-Queries] Perl module
* [https://github.com/sonicsnes/node-gamedig GameDig] Javascript (Node.JS) module
* [http://sourceforge.net/projects/srcdspy/ SRCDSpy] Python library
* [http://search.cpan.org/~masanorih/ Net-SRCDS-Queries] Perl module
* [https://github.com/linKhehe/a2squery a2squery] Python library
* [https://github.com/TronPaul/srcdspy SRCDSpy] Python library
* [http://github.com/frostschutz/SourceLib SourceLib] Python library
* [http://github.com/frostschutz/SourceLib SourceLib] Python library
* [http://www.codeproject.com/KB/game/Game_Server_Query_DLL.aspx aQuery] VB.NET library
* [http://github.com/Holiverh/python-valve python-valve] Python library
* [https://github.com/big-oh404/src_l4d2_query Left4Query] 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
* [https://github.com/atomy/sourcestats/ SourceStats] Source Server Statistics
* [https://github.com/atomy/sourcestats/ SourceStats] Source Server Statistics
* [https://github.com/xPaw/PHP-Source-Query-Class PHP Source Query] PHP library
* [https://github.com/xPaw/PHP-Source-Query-Class PHP Source Query] PHP library
* [https://github.com/cemahseri/SteamQuery.NET SteamQuery.NET] .NET/C# Wrapper (Built in .NET 9/.NET Standard 2.0, by cemahseri. Supports Source, GoldSource, and obsolete GoldSource protocols.)
* [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)
* [http://www.codeproject.com/KB/game/Game_Server_Query_DLL.aspx aQuery] VB.NET library
* [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).
* [https://github.com/gnif/SteamQueryProxy SteamQueryProxy] Extremely high performance protocol proxy written in pure C for Linux (Can be used to mitigate VSE DoS attacks, supports Source & GoldSource).
* [https://github.com/Svarrogh1337/Steam2Go Steam2Go] Golang library. Includes support for A2S, rcon and various WebAPI services.
* [https://github.com/hugmouse/objc-sourcequery ObjC Source Query] ObjC implementation of the Source Engine Query Protocol + Valve Master Server queries.


= See Also =
== See also ==


* [[Master Server Query Protocol]]
* [[Master Server Query Protocol]]
* [[Source RCON Protocol]]
* [[Source RCON Protocol]]
[[Category:Networking]]
[[Category:Networking]]
[[Category:Technical]]
[[Category:Technical]]
[[Category:Dedicated Server]]

Latest revision as of 00:16, 13 August 2025

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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.

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 up to 1400 bytes + IP/UDP headers. If a request or response needs more packets for the data it starts the packets with an additional header.

2023-07-10: Rust has been observed breaking this, sending packets up to the maximum IP size (64KB).

Simple Response Format

Data Type Comment
Header long Always equal to -1 (0xFFFFFFFF). Means it isn't split.
Payload

Multi-packet Response Format

Goldsource Server

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).
Payload

Source Server

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 Wikipedia icon 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.
This is only present in the first packet of the response and only if the response is being compressed.
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 BZ2_bzBuffToBuffDecompress() in C, bzdecompress() in PHP, or bz2.decompress() in Python. Compression appears to have been phased out in newer Source games, but is still present in ~2006-era engines.

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).

Note: Some titles when using the split packet method have been observed erroneously nesting the single message header inside the split payload.

Requests

The server responds to 5 queries:

A2S_INFO
Basic information about the server.
A2S_PLAYER
Details about each player on the server.
A2S_RULES
The rules the server is using.
A2A_PING
Ping the server. (DEPRECATED)
A2S_SERVERQUERY_GETCHALLENGE
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.

Challenge Mechanism

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 this post for more info.

Previously the structure of this document made it seem that only A2S_INFO messages would be responded with in this manner, however ANY of the queries made MAY result in a `S2C_CHALLENGE` response if either the challenge was omitted, is wrong, or has expired.

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

Data Type Value
Header byte 'T' (0x54)
Payload string "Source Engine Query\0"
Challenge long 4-byte challenge (sometimes -- see below) 
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:

FF FF FF FF 41 0A 08 5E EA

You need send :

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!

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

NOTE:some older titles have been observed sending the GoldSource INFO packet AND the newer INFO packet in reply to this.

Response Format

Note.pngNote:Both SiN 1 Multiplayer and Rag Doll Kung Fu utilise this response protocol.
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:
  • 'd' for a dedicated server
  • 'l' for a non-dedicated server
  • 'p' for a SourceTV relay (proxy)
Environment byte Indicates the operating system of the server:
  • 'l' for Linux
  • 'w' for Windows
  • 'm' or 'o' for Mac (the code changed after L4D1)
Visibility byte Indicates whether the server requires a password:
  • 0 for public
  • 1 for private
VAC byte Specifies whether the server uses VAC:
  • 0 for unsecured
  • 1 for secured
These fields only exist in a response if the server is running The Ship:
Data Type Comment
Mode byte Indicates the game mode:
  • 0 for Hunt
  • 1 for Elimination
  • 2 for Duel
  • 3 for Deathmatch
  • 4 for VIP Team
  • 5 for Team Elimination
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.
Only if if ( EDF & 0x80 ) proves true:
Data Type Comment
Port short The server's game port number.
Only if if ( EDF & 0x10 ) proves true:
Data Type Comment
SteamID long long Server's SteamID.
Only if if ( EDF & 0x40 ) proves true:
Data Type Comment
Port short Spectator port number for SourceTV.
Name string Name of the spectator server for SourceTV.
Only if if ( EDF & 0x20 ) proves true:
Data Type Comment
Keywords string Tags that describe the game according to the server (for future use.)
Only if if ( EDF & 0x01 ) proves true:
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.pngNote:Rag Doll Kung Fu servers always return 0 for "Server type."


Example response for Counter-Strike: Source: 

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: 

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: 

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: 

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.

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:
  • 'D' for dedicated server
  • 'L' for non-dedicated server
  • 'P' for a HLTV server
Environment byte Indicates the operating system of the server:
  • 'L' for Linux
  • 'W' for Windows
Visibility byte Indicates whether the server requires a password:
  • 0 for public
  • 1 for private
Mod byte Indicates whether the game is a mod:
These fields are only present in the response if "Mod" is 1:
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:
  • 0 for single and multiplayer mod
  • 1 for multiplayer only mod
DLL byte Indicates whether mod uses its own DLL:
  • 0 if it uses the Half-Life DLL
  • 1 if it uses its own DLL
VAC byte Specifies whether the server uses VAC:
  • 0 for unsecured
  • 1 for secured
Bots byte Number of bots on the server.
Note.pngNote:HLTV servers may respond with a late request that is either incomplete or incorrect if the number of slots is 255.


Example response: 

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.pngNote:SourceTV does not respond to this request.

Request Format

Data Type Value
Header byte 'U' (0x55)
Challenge int Challenge number, or -1 (0xFFFFFFFF) to receive a challenge number.

Challenge response format:

Data Type Value
Header byte 'A' (0x41)
Challenge int Challenge number.

Example challenge request: 

FF FF FF FF 55 FF FF FF FF                         ÿÿÿÿUÿÿÿÿ"

Example challenge response: 

FF FF FF FF 41 4B A1 D5 22                         ÿÿÿÿAÿÿÿÿ"

Example A2S_PLAYER request with the received challenge number: 

FF FF FF FF 55 4B A1 D5 22                         ÿÿÿÿUÿÿÿÿ"

Response Format

Data Type Comment
Header byte Always equal to 'D' (0x44)
Players byte Number of players whose information was gathered.
For every player in "Players" there is this chunk in the response:
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):

Data Type Comment
Deaths long Player's deaths
Money long Player's money
Note.pngNote: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.pngWarning: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.



Example response: 

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: 

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 variables included are the ones marked with FCVAR_NOTIFY as well as any additional ones listed in the server configuration.

Request Format

Data Type Value
Header byte 'V' (0x56)
Challenge long Challenge number, or -1 (0xFFFFFFFF) to receive a challenge number.

Challenge response format:

Data Type Value
Header byte 'A' (0x41)
Challenge long Challenge number.

Example challenge request: 

FF FF FF FF 56 FF FF FF FF                         ÿÿÿÿVÿÿÿÿ"

Example challenge response: 

FF FF FF FF 41 4B A1 D5 22                         ÿÿÿÿVK¡Õ"
Warning.pngWarning: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: 

FF FF FF FF 56 4B A1 D5 22                         ÿÿÿÿVK¡Õ"

Response Format

Note.pngNote:Responses to this query are usually multi-packeted.
Data Type Comment
Header byte Always equal to 'E' (0x45)
Rules short Number of rules in the response.
For every rule in "Rules" there is this chunk in the response:
Data Type Comment
Name string Name of the rule.
Value string Value of the rule.

A2A_PING

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

Warning.pngWarning:According to Valve (see 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

Data Type Value
Header byte 'i' (0x69) 
FF FF FF FF 69                                     ÿÿÿÿi

Response Format

Goldsource Server
Data Type Value
Header byte 'j' (0x6A)
Payload string Null 
FF FF FF FF 6A 00                                  ÿÿÿÿj.
Source Server
Data Type Value
Heading byte 'j' (0x6A)
Payload string '00000000000000.' 
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 -1 (0xFFFFFFFF) 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

Data Type Value
Header byte 'W' (0x57) 
FF FF FF FF 57                                     ÿÿÿÿW

Response Format

Data Type Comment
Header byte Should be equal to 'A' (0x41.)
Challenge long The challenge number to use.

Example response: 

FF FF FF FF 41 4B A1 D5 22                         ÿÿÿÿAK¡Õ"

Implementations

See also

Retrieved from "https://developer.valvesoftware.com/w/index.php?title=Server_queries&oldid=487032"