Problem with sending updates to a local server

I'm trying to send updates to a local Traccar server (running via IntelliJ on Windows 10), but the port seems to be closed no matter what I do.

• The PC running the server and the mobile device running the Traccar client are both connected to the same Wi-Fi.
• I created an inbound rule to enable port 5055 over TCP.
• The mobile device pings the PC IP successfully.
• netstat command shows that the port (actually all of the Traccar ports) is listening without specifying IP, for example: TCP [::]:5055 [::]:0 LISTENING.

The Traccar client fails to send. The port check in the website doesn't seem to be relevant as long as I'm trying to access the server via LAN (without modifying router settings, which I'm trying to avoid). Obviously the port wasn't available to devices on the network out of Traccar as well.
I managed to do it a few months ago, but can't figure out the current issue. Any help will be appreciated. Thanks!

1. Have you registered device on the server side?

2. Try opening URL on the phone:

http://your.server.ip:5055

Thanks for your response.

1. Yes, although I'd expect to see connection logs anyway, but there are none.
2. There's a timeout ("This site can't be reached").

If there is timeout it probably means some network issue or server is not running.

My bad - the mobile device wasn't connected to the Wi-Fi. It's now connected and I receive 404 error ("This x.x.x.x page can't be found").

Now that means that you are not connecting to Traccar.

Okay, so what issue may it be? Is there a chance that some other process is using that port?

When the server is NOT running and I go to localhost:5055 on PC, there's a "This site can't be reached" (so nothing is listening).
When the server is running and I go to localhost:5055, there's just a white blank page (maybe it's a 400 response which indicates that the server is listening but doesn't know how to handle HTTP requests?).

Do you have any idea? I'm a bit lost here.

Blank response with error code 400 is the right one. Why did you say 404 before?

Now everything should work. If it doesn't, check status screen and logs again.

400 is on the PC that is running the server (localhost). 404 is on the mobile device.
Meaning that the port is available locally only(?).

It means there is some network issue. Clearly your phone is connecting to some other server, not Traccar.

Eventually the PC wasn't discoverable to other devices on the network. I saw yesterday that the PC is actually listed on another PC's network devices list and therefore didn't look for it in Settings, but apparently it doesn't guarantee that the PC is actually discoverable. Maybe it's listed there because it was previously discoverable, but anyway I find it a bit strange.

Anyway, to solve it, go to Widows Settings -> Network & Internet -> Status -> Change connection properties -> Make this PC discoverable.

Thanks a lot for your help!