function doPost(e) {
  var json = {};
  try {
    if(typeof(e.postData) !== "undefined") {
      if(typeof(e.postData.contents) !== "undefined") {
        var contents = e.postData.contents;
        var obj = JSON.parse(contents);
        if (!isEmptyObject(obj)) {
          if(obj.hasOwnProperty("mac")) {
            var mac = obj["mac"];
            delete obj["mac"];
            setSpreadSheetUrl(mac);
            if (!isEmpty(spreadSheetUrl)) {
              if(obj.hasOwnProperty("msg")) {
                var message = obj["msg"];
                delete obj["msg"];
                switch(message) {
                  case "CREATE":
                    createSheets(obj);
                    resetDebugSheet();
                    break;
                  case "INIT":
                    var json = getInitData();
                    break;
                  case "REPORT":
                    saveBeacons(obj);
                    logDebug(obj);
                    break;
                  case "ALARM":
                    raiseAlarm();
                    break;
                  default:
                    break;
                }
              }
            }
          }
        }
      }
    }
  } catch(error) {
    Logger.log(error);
  }
  return ContentService.createTextOutput(JSON.stringify(json)).setMimeType(ContentService.MimeType.JSON);
}