Ping a server from client PC?

Kimochi · #1 (**permalink**) Mar 26th, 2007, 17:04

I've been trying to write a script using AJAX that will ping a foreign server from the client PC and then return the ping time in ms. I'm having no luck; the only time it works is if I'm connecting to a file on the save server, and that's not much use is it? It will almost always return 0.

Could somebody help me out? The servers I will be pinging are my own, so is there something I can do to let the client's browser know I'm pinging a friendly server? I thought of using subdomain DNS, but haven't tested that yet as my current web host is too nasty to let me do that

Thanks for any help!

Code: Select all

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Javascript & Ajax Ping</title>
<script type="text/javascript">
function ping()
{
  dt = new Date();
  if(window.XMLHttpRequest)
  {
      obj = new XMLHttpRequest();
      obj.open("GET", "http://rapidgameservers.com/serversubdomain", true);       
      obj.send(null);
  } 
  else if(window.ActiveXObject)
  {
      obj = new ActiveXObject("Microsoft.XMLHTTP");
      obj.open("GET", "http://rapidgameservers.com/serversubdomain", true);
      obj.send(null);
  } 
      
    ndt = new Date();
    time = (ndt-dt)/1000+"ms";
    alert(time);
}
</script>
</head>

<body onload="ping()">
</body>
</html>

spinal007 · #2 (**permalink**) Mar 27th, 2007, 01:48

The reason you keep getting 0 is because you haven't defined a callback function... I'm not good at explaining but I hope you get this.

The following line sends the request:

obj.send(null);

then the code continues to execute line by line before the response is received. meaning this code...

ndt = new Date();
time = (ndt-dt)/1000+"ms";
alert(time);

... is being processed immediately after the request is sent, not when the response is received, which is what you want.

What you're missing is what is sometimes called a 'callback' function. That is a function which is executed once the request is complete (the response is received)

obj.onreadystatechange = callbackFunctionName;

I haven't tested it, it should look like this:

Code: Select all

function ping()
{
  dt = new Date();

 // callback function to be executed and request is complete

      callback = function()  {
     ndt = new Date();
     time = (ndt-dt)/1000+"ms";
     alert(time);
    }

   if(window.XMLHttpRequest)
  {
      obj = new XMLHttpRequest();
      obj.open("GET", "http://rapidgameservers.com/serversubdomain", true);       
  } 
  else if(window.ActiveXObject)
  {
      obj = new ActiveXObject("Microsoft.XMLHTTP");
      obj.open("GET", "http://rapidgameservers.com/serversubdomain", true);
  } 

     // specify callback function

       obj.onreadystatechange = callback;

      obj.send(null);
}

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Ping a server from client PC?