gistfile1.js

window.navigator.mozSetMessageHandler('connection', 
  function onConnected(request) {
   var keyword = request.keyword;
   var port = request.port;
 
   port.onmessage = function onReceivedMessage(evt) {
     // this is the message you sent
     var message = evt.data;
     // do whatever you want to do later
   };
});