You need to use the SEF NETWORK to do that, make sure you're include this line in index.html
<object id='pluginObjectNetwork' classid='clsid:SAMSUNG-INFOLINK-NETWORK' style='opacity:0.0; background-color:#000000;width:0px;height:0px;'></object>
Then somewhere in your code you can use function:
var GetIPAddress = function(){
var network = document.getElementById('pluginObjectNetwork');
return network.GetIP(network.GetActiveType());
};
More information can be read at samsung docs: http://samsungdforum.com/Guide/ref00014/sef_plugin_network.html