Failed to connect to localhost port 80: Connection refused

Unity WWW class can connect to outside servers, but cannot connect to localhost. I have a crossdomain.xml in the localhost root. It is the PHP.EXE built in web server. It does work with other browsers. Unity 5.3.0f4

Can you help me why it doesn't work?

public class AppManager : MonoBehaviour {

 public string url = "http://localhost";
 public Text Result;
 public Text Error;

 void Start() {
     StartCoroutine(CallURL());
 }

 IEnumerator CallURL() {
     WWW www = new WWW(url);
     print("www started");
     yield return www;
     print(www.error);
     print(www.text);
     Result.text = www.text;
     Error.text = www.error;
 }

}