IPHostEntry ipHostEntry = Dns.GetHostEntry(ipString); // any ip string from external service, e.g. "localhost"
                IPAddress[] ipAddresses = ipHostEntry.AddressList; // count is 2. second is 127.0.0.1
                IPAddress ipAddress = ipAddresses.First(); // {::1}
                // Ip address will be something like http://[::1]:1234