function loadXMLDoc() {
  var method = "POST";
  var url = "../sms/xml.php";
  if(window.XMLHttpRequest) {
    req = new XMLHttpRequest();
    req.onreadystatechange = processReqChange;
    req.open(method, url, true);
    req.send(null);
  } else if (window.ActiveXObject) {
    req = new ActiveXObject("Microsoft.XMLHTTP");
    req.onreadystatechange = processReqChange;
    req.open(method, url, true);
    req.send();
  }
  setTimeout(function(){ loadXMLDoc(); }, 180000);
}
function processReqChange() {
  if(req.readyState == 4) {
    if(req.status == 200) {
      var output = document.getElementById( "sms_list" );
      output.innerHTML = req.responseText;
    } //else alert("Error retrieving the XML data:\n" + req.statusText);
  }
}