XMLHttpRequest read progressive data not working?

Question

I'm having issues with XMLHttpRequest downloading progressive data. I get a state 2 and than state 3. After state 3 it never gets called again... What am I doing wrong? I read somewhere I need to flush the data but how do I do that?

Here is my code:

    var xmlHttp = new XMLHttpRequest();
    // try to connect to the server
    try
    {
      // initiate server request
      xmlHttp.open("GET", "http://208.43.121.133:8164/;", true);
      xmlHttp.setRequestHeader("Icy-Metadata", "1");
      xmlHttp.onreadystatechange = function() 
      {
          alert("status: "+xmlHttp.status);
          alert("State: "+xmlHttp.readyState);

          if (xmlHttp.readyState == 3)
        {
            alert(xmlHttp.responseText);
        }
      };
      xmlHttp.send(null);
    }
    // display an error in case of failure
    catch (e)
    {
      alert("Can't connect to server:\n" + e.toString());
    }

Answer 1

The problem is most likely with this segment:

    if(xmlHttp.readyState == 3) {
        alert(xmlHttp.responseText);
    }

The reason being is that the xmlRequest isn't complete yet (readyState=4 when complete). When you requested the responseText prematurely, it triggered an error and stopped the code from finishing.

So you would change it to:

if(xmlHttp.readyState == 4) {
    alert(xmlHttp.responseText);
}

Answer 2

Kranu is correct, you're not allowed to read responseText when readyState is 3. See http://www.davidflanagan.com/2005/08/xmlhttprequestreadystate-3.html

The solution is to send a message at a time. When you receive one message, just make another XHR. That's how google does (did?) server push.