Getting IP Address From Client

I have an asp app we use to collect data. I did not write this and I know nothing about asp, however I am tasked with modifying the app. I am trying to collect the ip address of the client and put it in a text box. First piece of code is where I added the new text box.

Code:
<tr><td>Facility:</td><td><input id="facility" onfocus="processgetip(event)" /></td></tr>

I then created a function named processgetip

Code:
function processgetip(event) {
// Within this function, make an AJAX call to get the IP Address
$.ajax('@Url.Action("GetIPAddress","getipaddress")', function (ip) {
// When this call is done, your IP should be stored in 'ip', so
// You can use it how you would like
// Example: Setting a TextBox with ID "YourElement" to your returned IP Address
$("#facility").val(ip);
});
}

I then created a controller named getipaddress:

Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;

[code]...

Now with all of that it will compile and run using the localhost but it's not working. Not getting any errors it just doesn't return anything.