I’m trying to get ST to start and keep getting errors to the effect of 127.0.0.1 refused to connect.
I’ve gotten the same error in FireFox, Vivaldi, and Plasma. However in Konsole, I can ping both 127.0.0.1 and localhost with no errors
The system is a Debian/Linux box, running KDE.
I did some searching and I’m not finding anything that seems directly relevant.
Any idea where I should start looking?
Thanks, ex-Gooserider
You need to show some details, like output from starting Syncthing. My guess is Syncthing is not running.
Please try http://localhost:8384/ to see if the Syncthing GUI is running. Since localhost and 127.0.0.1 both point back to your existing machine, it should be able to ping itself.
If that doesn’t work, try ps -ef | grep syncthing to see if the Syncthing processes are running.
Sorry to not to have gotten back on this sooner - life has been excessively busy…
outputs from trying things in Konsole
@fancybox:~$ ps -ef | grep syncthing
atorrey 1067362 1066955 0 22:01 pts/0 00:00:00 grep syncthing
@fancybox:~$syncthing
[start] 22:01:48 INFO: syncthing v1.19.2-ds1 "Fermium Flea" (go1.19.8 linux-amd64) debian@debian 2023-04-09 10:47:16 UTC
[start] 22:01:48 WARNING: Failed to initialize config: config file version (37) is newer than supported version (36). If this is expected, use --allow-newer-config to override.
[monitor] 22:01:48 INFO: Syncthing exited: exit status 1
[start] 22:01:49 INFO: syncthing v1.19.2-ds1 "Fermium Flea" (go1.19.8 linux-amd64) debian@debian 2023-04-09 10:47:16 UTC
[start] 22:01:49 WARNING: Failed to initialize config: config file version (37) is newer than supported version (36). If this is expected, use --allow-newer-config to override.
[monitor] 22:01:49 INFO: Syncthing exited: exit status 1
[start] 22:01:50 INFO: syncthing v1.19.2-ds1 "Fermium Flea" (go1.19.8 linux-amd64) debian@debian 2023-04-09 10:47:16 UTC
[start] 22:01:50 WARNING: Failed to initialize config: config file version (37) is newer than supported version (36). If this is expected, use --allow-newer-config to override.
[monitor] 22:01:50 INFO: Syncthing exited: exit status 1
[start] 22:01:51 INFO: syncthing v1.19.2-ds1 "Fermium Flea" (go1.19.8 linux-amd64) debian@debian 2023-04-09 10:47:16 UTC
[start] 22:01:51 WARNING: Failed to initialize config: config file version (37) is newer than supported version (36). If this is expected, use --allow-newer-config to override.
[monitor] 22:01:51 INFO: Syncthing exited: exit status 1
[monitor] 22:01:52 WARNING: 4 restarts in 4.113507379s; not retrying further
fancybox:~$ syncthing --version
syncthing v1.19.2-ds1 "Fermium Flea" (go1.19.8 linux-amd64) debian@debian 2023-04-09 10:47:16 UTC
I may not be doing the right syntax, but “ping localhost” gets a response, but "ping localhost:8384, or any "ping http:// gets “Name or service not known”
The thing about version may be my problem? it appears to be the version from the Debian repo, not the latest…
ex-Gooserider
Looks like the version may have been the issue - I just followed the apt update configuration instructions https://apt.syncthing.net/ and it appears that this may gotten things working…
fancybox:~$ syncthing --version
syncthing v1.29.0-rc.1 "Gold Grasshopper" (go1.23.4 linux-amd64) debian@github.syncthing.net 2024-12-09 07:32:15 UTC [noupgrade]
It now appears to start… 
However the two machines I usually sync with are showing disconnected, which is probably not a totally bad thing given how long it’s been since they synced… There are probably files that now only exist on one or the other, and / or files that have different versions on the two machines.
Is there a good way to get the machines back in sync without causing to much in the way of conflicts? I seem to recall something about setting one to read only or something like that?
ex-Gooserider
At some point in the past you ran a version newer than Syncthing 1.19.2, so it generated a configuration file that isn’t compatible with the older version that you’re now trying to run.
ping is a simple tool for sending out a network “echo” – like a submarine sending out an audio pulse and waiting for its echo.
The basic syntax for ping is:
ping <Hostname|IP address>
So a hostname…
ping one.one.one.one
… or IP address:
ping 1.1.1.1
But not ping 1.1.1.1:8384, ping http://1.1.1.1/, ping http://one.one.one.one/, etc.
(For more details about “localhost”: Wikipedia – localhost)
Generally speaking, localhost – aka. 127.0.0.1 – is always going to respond to a ping because you’re talking to the operating system. You’re not talking to any applications so it really won’t tell you if Syncthing is listening.
Instead of ping, use cURL:
curl -I http://localhost:8384/
curl -I http://127.0.0.1:8384/
Note how it’s the same addresses used in a web browser. The -I asks cURL to retrieve only the HTTP headers (seeing the 1,000+ lines of HTML isn’t necessary for a quick check).
Was going to point you to apt.syncthing.net, but you were already a step ahead. 
If you know which machine holds the versions of files you want, and the other is expendable, then setting the machine you want to “Send Only” and the other to “Receive Only”, then when prompted about overriding local changes on the receive-only machine, accept the override.
But if you aren’t sure if there are important files you may want from both machines, you’re better off dealing with any conflicts.
As always, it’s best to have reliable backups first before moving forward.