Running btest server on ROS v6.38 (current, stable) and btest.exe v0.1 on Win10 (64-bit), wirelessly between Win client and ROS AP, causes ROS log entry "login failure for user admin via bandwidth-test".
The admin account exists and works for everything else (winbox/http/etc).
On the btest.exe client (also run as administrator) side it shows "running..." for a ~two seconds and then "disconnected".
Entering the wrong credentials causes "auth failed" and disabling authentication doesn't change issue from "running..." for a ~two seconds and then "disconnected".
No firewall rules, so port UDP port 2000 (default) not blocked, antivirus/firewall disabled on Win, and even if it did the error message would be wrong, especially since ROS is able to log the event.
Client works to public btest servers http://forum.mikrotik.com/viewtopic.php?f=2&t=104266 (however only if using direction "both", not "receive" or "send", strange)