Difference between revisions of "How to query a CS Server"

Revision as of 10:46, 11 September 2006

If you want to e.g. get the number and names of all player who are currently playing on a CS-server, you have to send a so-called "query" to this server (using UDP) and handle everything the server sends back to you. This isn't as easy as it sounds. At first, you would have to 'learn', or, at least, understand the protocol a CS-server uses (e.g. what do I have to send to the server to get a 'good' reply and what's the structure of this reply). If you want to learn more about these protocols, take a look at http://dev.kquery.com/ or http://www.valve-erc.com/srcsdk/Code/Networking/serverqueries.html.

The following script echos the output to your active window. You will have to modify it to be able to use it as 'bot'. It's a more complex script and you don't need to understand it (completely) to be able to use it.

; HL server query snippet by Saturn
;
; usage:
; /hlinfo <ip> <port>
; /hlplay <ip> <port>

; the alias that opens a new socket if you want to get general information about a running CS-server
alias hlinfo {
  ; using a dynamic socket name so we can use multiple instances at once
  var %sock = $+(hlinfo-,$ticks)
  ; actually open the socket
  sockudp -k %sock $1-2 $str($chr(255),4) $+ TSource Engine Query
  ; closing the socket after 60seconds if there is no response (else it will be closed by another event (see below))
  .timer $+ %sock 1 60 sockclose %sock
}

; this event will get all data sent back from the server
on *:UDPREAD:hlinfo-*:{
  ; save it in a binary variable
  sockread -f &reply

  ; set some local variables that we will use below
  var %offset, %name, %map, %game, %num, %max, %ip, %dir
 
  ; following the protocol, this "m" shows us that we queried a Half-Life 1 server
  if ($chr($bvar(&reply,5)) == m) {
    ; Half-Life 1 info reply
    
    %offset = 6
 
    ; save the ip
    %ip = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%ip) + 1)
   
    ; the same
    %name = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%name) + 1)

    ; the current map
    %map = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%map) + 1)

    ; the game directory
    %dir = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%dir) + 1)

    ; the name of the game
    %game = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%game) + 1)

    ; current and maximum players
    %num = $bvar(&reply,%offset)
    %max = $bvar(&reply,$calc(%offset + 1))
  }

  ; else we get data for a CS:Source game
  else {
    ; Source info reply
    ; we do the same as above
    %offset = 7

    %name = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%name) + 1)

    %map = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%map) + 1)

    %dir = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%dir) + 1)

    %game = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%game) + 1)

    %num = $bvar(&reply,$calc(%offset + 2))
    %max = $bvar(&reply,$calc(%offset + 3))
  }
 
  ; now we echo all stored details to the active window
  echo -a Info for $sock($sockname).saddr $+ : $+ $sock($sockname).sport
  echo -a Name: %name
  echo -a Map: %map
  echo -a Game: %game
  echo -a Players: %num $+ / $+ %max
  
  ; and turn off the timer closing the socket
  .timer $+ $sockname off
  ; as we can close it now manually
  sockclose $sockname
}


; this is the alias that will be called from hlplay to open the socket 
alias hlchal {
  ; $1 = ip, $2 = port, $3- = what to call when received
  ; use dynamic socket name as above
  var %sock = $+(hlchal-,$ticks)
  ; open the socket
  sockudp -k %sock $1-2 $str($chr(255),4) $+ W 
  ; mark it with the ip and port (and the query we want to call when we've received something from the server)
  sockmark %sock $3- $1-2
  ; and make a new timer to close it after 60 seconds
  .timer $+ %sock 1 60 sockclose %sock
}

; read everything that comes back from the hlchal-* query
on *:UDPREAD:hlchal-*:{
  ; and save it in the binary variable called &reply
  sockread -f &reply
  ; actually call the alias saved in the sockmark (hlplay_query)
  $sock($sockname).mark $bvar(&reply,6,4)
  ; and turn the timer off because we can close it manually
  .timer $+ $sockname off
  sockclose $sockname
}

; the alias we can call to make everything easier 
; it will call other aliases to open sockets etc.
alias hlplay {
  hlchal $1-2 hlplay_query
}

; the alias that opens the _real_ socket to receive data (everything before was just to challenge the server (read the website mentioned above))
alias hlplay_query {
  ; set a binary variable
  bset &query 1 255 255 255 255 85 $3-
  ; use dynamic socket names again
  var %sock = $+(hlplay-,$ticks)
  ; open the socket
  sockudp -k %sock $1-2 &query
  ; and turn on the timer closing the socket after 60seconds
  .timer $+ %sock 1 60 sockclose %sock
}

; this event will receive all data from the server as response to our query
on *:UDPREAD:hlplay-*:{
  ; we save it in &reply
  sockread -f &reply
 
  ; set some local variables we will use later
  var %i = 1, %num = $bvar(&reply,6), %offset = 7
  var %count = 0, %name, %kills

  ; and echo the number of players
  echo -a Players on $sock($sockname).saddr $+ : $+ $sock($sockname).sport

  ; now we can loop through all player and save some details about them
  while (%i <= %num) {
    inc %offset
  
    ; the name
    %name = $bvar(&reply,%offset,128).text
    inc %offset $calc($len(%name) + 1)

    ; the kills
    %kills = $bvar(&reply,%offset).long
    if ($isbit(%kills,32)) dec %kills $calc(2^32)
    inc %offset 8

    ; and if there was a player
    if (%name != $null) {
      ; increase the variable that shows us the number of the player
      inc %count
      ; and echo it to the active window with the kills saved above
      echo -a %count $+ . %name - %kills
    }
 
    ; increase %i so we go on with the next player
    inc %i
  }
 
  ; if there are no players online, echo it aswell
  if (%count == 0) echo -a No players found!

  ; turn off the timer
  .timer $+ $sockname off
  ; and close the socket manually
  sockclose $sockname
}