Firefox can’t connect to the server at 127.0.0.1:8384

Support
1

i can’t run my syncthing. i also tried installing latest version and its stil not working, log below.

2026-04-06 04:51:04 INF syncthing v2.0.15 "Hafnium Hornet" (go1.25.7 windows-amd64) builder@github.syncthing.net 2026-02-11 10:41:38 UTC (log.pkg=main)
2026-04-06 04:51:04 INF Calculated our device ID (device=TU7PPMC-LD5QSLK-7J5RCDE-L5EBNKD-SIQXKMT-WZ37KNN-RTWWPEP-RTJJ2QJ log.pkg=syncthing)
2026-04-06 04:51:04 INF Overall rate limit in use (send="is unlimited" recv="is unlimited" log.pkg=connections)
2026-04-06 04:51:04 ERR Skipping malformed listener URL (uri=127.0.0.1:8385 error="parse \"127.0.0.1:8385\": first path segment in URL cannot contain colon" log.pkg=connections)
2026-04-06 04:51:04 INF Using discovery mechanism (identity="global discovery server https://discovery-lookup.syncthing.net/v2/?noannounce" log.pkg=discover)
2026-04-06 04:51:04 INF Using discovery mechanism (identity="global discovery server https://discovery-announce-v4.syncthing.net/v2/?nolookup" log.pkg=discover)
2026-04-06 04:51:04 INF Using discovery mechanism (identity="global discovery server https://discovery-announce-v6.syncthing.net/v2/?nolookup" log.pkg=discover)
2026-04-06 04:51:04 INF Using discovery mechanism (identity="IPv4 local broadcast discovery on port 21027" log.pkg=discover)
2026-04-06 04:51:04 INF Using discovery mechanism (identity="IPv6 local multicast discovery on address [ff12::8384]:21027" log.pkg=discover)
2026-04-06 04:51:04 INF Ready to synchronize (folder.label=phoneCamera folder.id=21061110ag_c24y-photos folder.type=receiveonly log.pkg=model)
2026-04-06 04:51:04 ERR Failed to start API (error="listen tcp 127.0.0.1:8384: bind: An attempt was made to access a socket in a way forbidden by its access permissions." log.pkg=syncthing)
2026-04-06 04:51:04 ERR Failed to start API/GUI (error="listen tcp 127.0.0.1:8384: bind: An attempt was made to access a socket in a way forbidden by its access permissions." log.pkg=api)
2026-04-06 04:51:04 INF Ready to synchronize (folder.label=Obsidian folder.id=ajz6f-y6wl9 folder.type=sendreceive log.pkg=model)
2026-04-06 04:51:04 INF Ready to synchronize (folder.label=ToLaptop folder.id=havnq-bbxxd folder.type=sendonly log.pkg=model)
2026-04-06 04:51:04 INF Completed initial scan (folder.label=phoneCamera folder.id=21061110ag_c24y-photos folder.type=receiveonly log.pkg=model)
2026-04-06 04:51:04 INF Ready to synchronize (folder.label=Skrispi folder.id=kbeey-wyqgk folder.type=sendreceive log.pkg=model)
2026-04-06 04:51:04 INF Exiting (log.pkg=syncthing)
2

You’re getting some sort of permission error for listening on port 8384. I don’t know what that means. Some odd antivirus or firewall restriction?

There’s also a misconfiguration of the sync port listen address (the one you set to port 8385), something wrong with the format, but that’s secondary.

3

i didnt change any antivirus rules(i only use windows antivirus). I forgot to mention that i tried changing port but i revert it back to default since nothing changed.

edit : just restarted my pc and its fixed lol, i might be dumb haha