<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>5050</title>
<script type="text/javascript" src="http://code.jquery.com/jquery-1.11.0.js"></script>
</head>
<body>
<h1>5050</h1>
<button id="go">GO</button>
<script>
$("#go").click(() => {
let win = window.frames.bobnelson5051;
win.postMessage("from 5050 to 5051", "*");
});
</script>
<br>
<iframe src="http://localhost:5051/5051.html" name="bobnelson5051" height=500></iframe>
<pre id="out"></pre>
<script>
top.addEventListener("message", e => {
//debugger;
$("#out").text((_, t) => `${t}\n${e.data}`)
});
</script>
</body>
</html>