[Modify] Add it

websocket-sharp/Net/HttpListenerContext.cs

@@ -191,6 +191,14 @@ namespace WebSocketSharp.Net
                );
     }
 
+    private void sendAuthenticationChallenge (string challenge)
+    {
+      _response.StatusCode = 401;
+      _response.Headers.InternalSet ("WWW-Authenticate", challenge, true);
+
+      _response.Close ();
+    }
+
     #endregion
 
     #region Internal Methods