Rcon an Hl2-Server

[rey003]

Code:

    function _Write($cmd, $s1='', $s2='') { 
    // Get and increment the packet id 
    $id = ++$this->_Id; 

    // Put our packet together 
    $data = pack("VV",$id,$cmd).$s1.chr(0).$s2.chr(0); 
   echo $data;
    // Prefix the packet size 
    $data = pack("V",strlen($data)).$data; 
   echo "
".$data;
    // Send packet 
    fwrite($this->_Sock,$data,strlen($data)); 

    // In case we want it later we'll return the packet id 
    return $id; 
    }

Was passiert hier genau? besonders das pack versteh ich nicht.

Edit: die echos sind von mir^^