Redirect page into the subsite based on the URL string

Inside the Master page Head Tag enter the following Java script.
<script type="text/javascript">
   
var str="http://" + window.location.toString().split("//")[1].split("/")[0] + "/";


if(str=="http://servername/" || str=="http://servernamewithdomain/")
window.location.href = "http://servername:Port/sites/subsitename/SitePages/Home.aspx";


</script>