Perché mi da sempre tutti i campi "unknown"?

<html>
<script>
var myAddress=java.net.InetAddress.getLocalHost();

var host=myAddress.getHostName();

var ip=myAddress.getHostAddress();

function ciao(){

document.write("Your address: "+host+" ------------ ")

document.write("Your IP: "+ip)
}
</script>
<body onload="ciao()">
</body>
</html>

Thank's.
Zio Ciof (I'm learnig too slowly)....