call Web Service from C# application

Question

I've a simple Web Service getAD.asmx that I use to retrieve data from active directory. I need to execute WS as a specific user, and be sure that only corporate user could consume it, so I'm using Windows authentication and ASP.NET Impersonation.

I tried to add a local simple web form to test my service, and it seems to work correctly

getAD myWS = new getAD();
string testResult = myWS.test(); // testResult execute correctly

Now I'm trying to call the same service from another C# application, so I added a Web Reference and did the same call, but I get a 401 error (Unauthorized) with any user.

rbasws01.getAD myWS = new rbasws01.getAD();
string testResult = myWS.test(); // error 401, not authorized

Am I missing something?

EDIT: this is the code of my WebService

[WebService(Namespace = "http://myUri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.ComponentModel.ToolboxItem(false)]
public class getAD : System.Web.Services.WebService {

    [WebMethod]
    public string test() {
        return "Test positive";
    }
}

Answer 1

Try setting a localhost:[some-port-number] binding on your IIS and pointing your request of the webservice to that.

So instead of calling http://myUri.org/ws/something , call http://localhost:1234/ws/something from within your application.

IIS can be a bit funny sometimes about talking to itself - I read this is to prevent some kind of attacks, but never was able to find the link again! Thanks to @LeeHarrison, this is called Loopback Checking.

Another way of getting round this issue is to disable Loopback Checking as described in this KB Article .