Send the request by XMLHttpRequest

Sending request is the asynchronous operation ,here is the code of sending on the widget:

function getRequest() { 
    http_request = false;
    if(window.XMLHttpRequest)
    {
        http_request = new XMLHttpRequest();//create a new XMLHttpRequest()
        if (http_request.overrideMimeType)
        {//set MIME type
            http_request.overrideMimeType("text/xml");
            DEBUG("dDisp", "sendRequest","http_request is XMLHttpRequest!");
        }

    }
    else if(window.ActiveXObject)
    {
        try
        {
            http_request = new ActiveXObject("MSXml2.XMLHTTP");
            DEBUG("dDisp", "sendRequest","http_request is MSXml2.XMLHTTP!");
        }
        catch(e)
        {
            try
            {
                http_request = new ActiveXObject("Microsoft.XMLHTTP");
                DEBUG("dDisp", "sendRequest","http_request is Microsoft.XMLHTTP!");
            }
            catch(e)
            {
              DEBUG("dDisp", "sendRequest","http_request is not match!");}
            }
    }
    if(!http_request)
    {
        DEBUG("dDisp","sendRequest","Can't create XMLHttpRequest object "+http_request);
        return false; 
    }
   return http_request; 
}

/**
* send the request
*/    
function getResponseText(){
	
    DEBUG("dDisp","sendRequest","Start to open XMLHttpRequest ");
    var vurl = document.getElementById("serverUrl").value;
    DEBUG("dDisp", "GetResponseText","Input URL is: " + vurl); 
    DEBUG("dDisp","sendRequest","Start to open XMLHttpRequest ");
     	  try {
		 http_request = new XMLHttpRequest();
		 http_request.open("post",vurl,true);
 		 http_request.onreadystatechange = function(){//callback function
		if (http_request.readyState==4){
                           DEBUG("dDisp", "ResponseData", http_request.status+"-"+http_request.readyState); 
 			   DEBUG("dDisp", "getResponseHeader", http_request.getResponseHeader("Content-Type")); 
                           DEBUG("dDisp", "getResponseText", http_request.responseText); 
			}
		}
		 http_request.setRequestHeader("Content-Type", "text/xml")
		 http_request.setRequestHeader("charset", "GBK");        
		 http_request.setRequestHeader("Widget-IMEI", "102");        
		 http_request.setRequestHeader("Widget-Timeout", "20");  
                 http_request.setRequestHeader("Widget-Action","Report"); 

                 //reportXml content
                 var reportXml = "<WidgetScriptResultResp>";
		 reportXml += i;
     		 reportXml += "</WidgetScriptResultResp>";
                 DEBUG("dDisp", "Loop:", i);
		 http_request.send(reportXml);				
	      }
	  catch (e) {
	  	       DEBUG("dDisp","sendRequest","Failed to open XMLHttpRequest ");
		       break;
		     }	
	}
    DEBUG("dDisp","sendRequest","Finished!");
}

 onreadystatechange() is the callback function of XMLHttpRequest,you can hanld the response of web service. readyState :0--before the open();1--before the send();2--request have been sent.3--request are handling with.4--request have been done.