How to make a simple HTTP request from a visual?

I have been trying to integrate a request into one of my viusals and I'm having trouble getting it to work. I was hoping you might be able to help me out. I have a local server setup which I am requesting data from using a GET. I thought there might be a cross domain issue with the request, so I set up another local server and ran the same request from there and it worked. 

The body of the request is this: 

var xmlhttp = new XMLHttpRequest();
  xmlhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
        console.log(JSON.parse(xmlhttp.responseText))

    }
  };

xmlhttp.open("GET", "http://localhost:8090/vis_data?name&value", true);
xmlhttp.send();

The visual is running on port 8080, the data lives on port 8090, and to test the domain issues I ran the same request from port 8070, and it worked.

Can anyone help?

Thanks!