Yes, I used the build you linked to here:
index.php/topic,3982.msg23376.html#msg23376
It's a "random" ephemeral port, whichever windows says is next available:
10/18/2016 1:52:54 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: UDP/17566
10/18/2016 1:52:54 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: TCP/17566
10/18/2016 1:52:54 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: UDP/65509
10/18/2016 1:52:54 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: TCP_SSL/4433
10/18/2016 1:52:54 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: TCP/65509
10/18/2016 1:52:53 AM - qBittorrent is trying to listen on any interface port: 65509
another try:
10/18/2016 2:11:18 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: UDP/17708
10/18/2016 2:11:18 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: TCP/17708
... (same as before, the other 3 -- UDP/65509 + TCP_SSL/4433 + TCP/65509)
10/18/2016 2:11:17 AM - qBittorrent is trying to listen on any interface port: 65509
another try:
10/18/2016 2:15:07 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: UDP/17727
10/18/2016 2:15:07 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: TCP/17727
...
10/18/2016 2:15:06 AM - qBittorrent is trying to listen on any interface port: 65509
another try:
10/18/2016 2:16:48 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: UDP/17744
10/18/2016 2:16:48 AM - qBittorrent is successfully listening on interface 0.0.0.0 port: TCP/17744
...
10/18/2016 2:16:47 AM - qBittorrent is trying to listen on any interface port: 65509
Notice the port keeps increasing? That's windows cycling through its ephemeral ports as I restart qBT.
TCP View is how I confirmed the port was being used by qBT and that it was whatever ephemeral port was next available.
qBT seems to be doing something for loopbacks on 127.0.0.1, as I see 2 of those as well as the listening port in TCP View.
Incidentally, the 2 connections on 127.0.0.1 seem to use ephemeral ports immediately before the Listening port that qBT mistakenly chooses.
qBT doesn't seem to do this every time, and I can't yet tell you how to repeat this...but if I had a guess, having all the Connections Limits disabled (under Options, Connection) along with disabling UPnP and disabling use different port on start may somehow be contributing factors.
I'd say currently I get the wrong listening port about 1 out of every 4 qBT launches.
I've even tested that qBT actually is listening on this port (instead of port 65509) using another BT client that I can "feed" torrents to qBT with, as I've demonstrated in my Extreme Speed Tests:
index.php/topic,3956.0.html
in qBittorrent.ini, there is this:
Connection\PortRangeMin=65509
...as I intended.
But no mention of any of the 17xxx ports it "randomly" choses sometimes.
Possibly related to this issue?:
https://github.com/qbittorrent/qBittorrent/issues/4617