qbittorrent-nox is installed on OpenBSD. I can access its WebUI from localhost, but can't from another machine - connection refused.

From another machine I can access pages served by httpd and python3 -m http.server 8000 and python3 -m http.server 8080 (the port used by qbittorrent-nox).
I can remotely access qbittorrent-nox that is installed on Linux in the same network setup.

I have 2 OpenBSD machines (a headless NAS and a laptop), both have qbittorrent-nox unreachable.

Any hints? Thank you

Update (the accepted answers):

from post #9 by @rvp, here edited by me:

rvp OpenBSD has a peculiarity which is explained in man 4 ip6.

When you open a listen-socket, you can choose to set an option called IPV6_V6ONLY. With this set to 0, an IPv6 server socket will listen on both IPv6 and IPv4 addresses.
Most programs set this to 0 so that they need not open 2 server sockets for the same port.

However, on OpenBSD, as the man-page explains:
IPV6_V6ONLY int *
      Get or set whether only IPv6 connections can be made to this socket. For wildcard
      sockets, this can restrict connections to IPv6 only. With OpenBSD IPv6 sockets are
      always IPv6-only, so the socket option is read-only (not modifiable).
So there you have it: I think (I haven't read the code, mind) that qbittorrent is setting that option to 0 when the WebUI\Address= field is * (listen on all), expecting the server will listen on both IPv6 & IPv4 addresses, but, this doesn't work on OpenBSD.

from post #11 by @rvp, here edited by me:

rvp one standard workaround for this is to add an IPv6 address (and an AAAA record in your DNS config) to the host running qbittorrent. This way, even if qbittorrent only listens on an IPv6 address, as long as clients use hostnames instead of IP addresses (and support IPv6) the connection will succeed.

What I have done so that it works for me, OP:

I have put localhost into ~/.config/qBittorrent/qBittorrent.conf:

WebUI\Address=localhost

and I get in ~/.local/share/qBittorrent/logs/qbittorrent.log:

(N) 2022-01-04T22:26:30 - Web UI: Now listening on IP: localhost, port: 8080

and now I can log into Web UI both from localhost and remotely.

This also works: from post #5:

uxer I put my LAN into ~/.config/qBittorrent/qBittorrent.conf:

WebUI\Address=192.168.88.*

and I got in ~/.local/share/qBittorrent/logs/qbittorrent.log:

(N) 2022-01-01T00:29:37 - Web UI: Now listening on IP: 192.168.88.*, port: 8080

and I could log into Web UI both from localhost and remotely.

(However, I am not actually sure that WebUI\Address=192.168.88.* opens access to 192.168.88.*. I tried being more specific feeding 192.168.88.10-192.168.88.254 range, and tested it by specifying a narrower 192.168.88.10-192.168.88.251 range, leaving my 252 machine out. I did 3 tries: 192.168.88.10-251; 192.168.88.10-192.168.88.251 and "192.168.88.10/31,192.168.88.12/30,192.168.88.16/28,192.168.88.32/27,192.168.88.64/26,192.168.88.128/26,192.168.88.192/27,192.168.88.224/28,192.168.88.240/29,192.168.88.248/30" (converter). Nope, I still could connect from 252. Dunno)