AddonSK: how can window from require('sdk/window/utils').openDialog interact with main.js script? - firefox-addon-sdk

Question

I am writing a FF addon SDK plugin.
My main.js opens a popup window with :
var win = require('sdk/window/utils').openDialog({
url:"http://www.example.com/index.html",
features: Object.keys({
resizable: true,
scrollbars: true
}).join(),
name: "myWin"
});
I need the window to send data to the main.js (index.html is an external HTTP classical html/JS page)

Answer 1

1: add a content script.
using pageMod or tabs API, inject a js file in to the http://www.example.com/index.html page.
2: sending message from the content script, then add an message listener in the main.js

Answer 2

In main.js:
var tab = win.tabs[0]; // as it is a pop-up window I assume it has only one tab
// attach content script to tab and access worker object
var worker = tab.attach({
contentScriptFile: self.data.url('popup_window_script.js'), // script from file
contentScript: '' // and/or script from string
});
// listen to worker / popup_window_script.js
worker.port.on('msg_from_popup_window_script_js', function ( msg ) {
// your code
});
// speak to worker / popup_window_script.js
worker.port.emit('msg_from_main_js', 'your message');
In popup_window_script.js:
// listen (to main.js)
self.port.on('msg_from_main_js', function ( msg ) {
// your code
});
// speak (to main.js)
self.port.emit('msg_from_popup_window_script_js', 'your message');