Client answered to 
<?xml version="1.0" encoding="UTF-8" ?>
<doc>
    <gateway>
      <name>smartpchelp.com</name>
      <path>/home/webadmin/smartpchelp.com/html/4sale/index.php</path>
      <url_path>/4sale/index.php</url_path>
      <remote>38.107.179.209</remote>
   </gateway>
<context>
<site_id>738</site_id>
<site_password>eee0074612ac19f602c40d4d65186179</site_password>
<lang>en_us</lang></context>

  <request>
    <request_type>list</request_type>
    <column> ping</column>
<ServerFunction>
<name>ping</name>
<parameters>
</parameters>
</ServerFunction>
  </request>
</doc>
by
HTTP/1.1 502 Bad Gateway
Server: nginx/0.7.67
Date: Sun, 20 May 2012 08:55:39 GMT
Content-Type: text/html
Content-Length: 173
Connection: close

<html>
<head><title>502 Bad Gateway</title></head>
<body bgcolor="white">
<center><h1>502 Bad Gateway</h1></center>
<hr><center>nginx/0.7.67</center>
</body>
</html>
©/Kaqoo