Session is a server side abstract based on an instance of a browser.
Tabs are fenced off from one another for security reasons, and the information is neither visible to other tabs nor available to the server.
What can be done is to utilize javascript's "window.name" property. It was designed more for opening new windows/tabs but by assigning a name to it after the connection is made. You would need to utilize then to validate the window.name before displaying content.
It has been a few years since I have worked with this and I unfortunately do no remember the code I had used.
Here is a Proof-of-Concept which does work in IE- running this from a local file will generate a script warning though.
<html>
<head>
<title>Test Window Name</title>
<script type ="text/javascript">window.name="MyWindowsName";</script>
</head>
<body>
<h1>
The name for this window is:
<script type ="text/javascript">document.write(window.name);</script>
</h1>
</body>
</html>
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