Limit Only One Session Per User In ASP.NET Mvc 4

<script type="text/javascript"> 
    var clicked = false;
    function CheckBrowser()
    {
        debugger;
        if (clicked == false)
        {
            //Browser closed
        }
        else
        {
            //redirected 
            clicked = false;
        }
    }
 
    function bodyUnload()
    {
        debugger;
        if (clicked == false)//browser is closed
        {
            debugger;
            var request = GetRequest();
           
            request.open("GET", "Logout", true);
            request.send();
        }
    }
 
    function GetRequest()
    {
        debugger;
        var request = null;
        if (window.XMLHttpRequest)
        {
            //incase of IE7,FF, Opera and Safari browser
            request = new XMLHttpRequest();
        }
        else
        {
            //for old browser like IE 6.x and IE 5.x
            request = new ActiveXObject('MSXML2.XMLHTTP.3.0');
        }
        return request;
    }

onunload="bodyUnload();" Onclick="clicked=true;