I want to get a value from included page if a button on the page is clicked to pop up box on tinymce plugin.

I try below codes. I have no idea how to make it possible because i am quite new to tinymce plugin. 

My plugin js file looks like,

tinymce.PluginManager.add('example2', function(editor, url) {
 editor.addButton('example2', {
 text: 'My button',
 icon: false,
 onclick: function() {
 editor.windowManager.open({
 title: 'TinyMCE site',
 url: 'https://jsfiddle.net/sawnmichele021/mjsm11fm/1/embedded/result,js,css',
 width: 400,
 height: 300,
buttons: [{
 text: 'Insert',
 onclick: function(){
 alert('hi');
 }
 }]
 
 });
 
 }
 });
});
tinymce.init({
 selector: "textarea",
 plugins: "example2",
 toolbar: "example2 undo redo | styleselect | bold italic | alignleft aligncenter alignright alignjustify | bullist numlist outdent indent | link image"
});

Could anybody else help me?