Can't connect to Windows device after updating to v2.0

Support Android
1

Android app continuously failing to connect to Windows syncthing instance.

But files actually sync in some attempts.

Enabling Root didn’t help.

If in Android, I disable all folders - it connects, if i add new folder it also connects.

If i enable old folders, it shows sync (some percent) and after a second disconnects.

I am using android app from Catfriend1. v2.0

I can provide more logs or screen recording if needed.

I have attached windows log.

syncthing.log (1.3 MB)

Android syncthing logs

2025-08-13 19:58:51 INF Lost device connection (kind=primary device=WZY3IKA connection=“[::]:22000-192.168.1.50:22000/quic-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P20-62RBE5AI8V4I69DDOVNEQB9HI8” error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” remaining=0 log.pkg=model) 2025-08-13 19:58:51 INF Connection closed (device=WZY3IKA connection=“[::]:22000-192.168.1.50:22000/quic-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P20-62RBE5AI8V4I69DDOVNEQB9HI8” error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” log.pkg=model) 2025-08-13 19:59:09 INF Established secure connection (device=WZY3IKA connection.local=192.168.1.13:22000 connection.remote=192.168.1.50:22000 connection.type=quic-server connection.lan=true connection.crypto=TLS1.3-TLS_AES_128_GCM_SHA256 connection.prio=20 connection.id=62RBE7GKTKAO27UJK55LN4IVFA log.pkg=connections) 2025-08-13 19:59:09 INF New device connection (device=WZY3IKA address=192.168.1.50:22000 remote.name=ServerSyncThing remote.client=syncthing remote.version=v2.0.0 log.pkg=model) 2025-08-13 19:59:10 INF Ignoring announced folder (folder.id=e2egz-zl49s device=WZY3IKA log.pkg=model) 2025-08-13 19:59:10 INF Established secure connection (device=WZY3IKA connection.local=“[::]:22000” connection.remote=192.168.1.50:22000 connection.type=quic-client connection.lan=true connection.crypto=TLS1.3-TLS_AES_128_GCM_SHA256 connection.prio=20 connection.id=62RBE7L38BOUA9OERBGH5FCO3C log.pkg=connections) 2025-08-13 19:59:10 INF Additional device connection (device=WZY3IKA address=192.168.1.50:22000 count=1 log.pkg=model) 2025-08-13 19:59:10 INF Lost device connection (kind=primary device=WZY3IKA connection=192.168.1.13:22000-192.168.1.50:22000/quic-server/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P20-62RBE7GKTKAO27UJK55LN4IVFA error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” remaining=1 log.pkg=model) 2025-08-13 19:59:11 INF Ignoring announced folder (folder.id=e2egz-zl49s device=WZY3IKA log.pkg=model) 2025-08-13 19:59:11 INF Lost device connection (kind=primary device=WZY3IKA connection=“[::]:22000-192.168.1.50:22000/quic-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P20-62RBE7L38BOUA9OERBGH5FCO3C” error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” remaining=0 log.pkg=model) 2025-08-13 19:59:11 INF Connection closed (device=WZY3IKA connection=“[::]:22000-192.168.1.50:22000/quic-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P20-62RBE7L38BOUA9OERBGH5FCO3C” error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” log.pkg=model) 2025-08-13 19:59:29 INF Established secure connection (device=WZY3IKA connection.local=192.168.1.13:22000 connection.remote=192.168.1.50:22000 connection.type=tcp-server connection.lan=true connection.crypto=TLS1.3-TLS_AES_128_GCM_SHA256 connection.prio=10 connection.id=62RBE9R1D9KGKM1LMFE3VK23OQ log.pkg=connections) 2025-08-13 19:59:29 INF New device connection (device=WZY3IKA address=192.168.1.50:22000 remote.name=ServerSyncThing remote.client=syncthing remote.version=v2.0.0 log.pkg=model) 2025-08-13 19:59:30 INF Ignoring announced folder (folder.id=e2egz-zl49s device=WZY3IKA log.pkg=model) 2025-08-13 19:59:30 INF Established secure connection (device=WZY3IKA connection.local=192.168.1.13:40038 connection.remote=192.168.1.50:22000 connection.type=tcp-client connection.lan=true connection.crypto=TLS1.3-TLS_AES_128_GCM_SHA256 connection.prio=10 connection.id=62RBE9VK920GEG4IRE1I6I97O6 log.pkg=connections) 2025-08-13 19:59:30 INF Additional device connection (device=WZY3IKA address=192.168.1.50:22000 count=1 log.pkg=model) 2025-08-13 19:59:30 INF Lost device connection (kind=primary device=WZY3IKA connection=192.168.1.13:22000-192.168.1.50:22000/tcp-server/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-62RBE9R1D9KGKM1LMFE3VK23OQ error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” remaining=1 log.pkg=model) 2025-08-13 19:59:31 INF Ignoring announced folder (folder.id=e2egz-zl49s device=WZY3IKA log.pkg=model) 2025-08-13 19:59:31 INF Lost device connection (kind=primary device=WZY3IKA connection=192.168.1.13:40038-192.168.1.50:22000/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-62RBE9VK920GEG4IRE1I6I97O6 error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” remaining=0 log.pkg=model) 2025-08-13 19:59:31 INF Connection closed (device=WZY3IKA connection=192.168.1.13:40038-192.168.1.50:22000/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-62RBE9VK920GEG4IRE1I6I97O6 error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” log.pkg=model) 2025-08-13 20:00:29 INF Established secure connection (device=WZY3IKA connection.local=192.168.1.13:22000 connection.remote=192.168.1.50:22000 connection.type=tcp-server connection.lan=true connection.crypto=TLS1.3-TLS_AES_128_GCM_SHA256 connection.prio=10 connection.id=62RBEGQHJBRH61NJ5Q7EOM69P4 log.pkg=connections) 2025-08-13 20:00:29 INF New device connection (device=WZY3IKA address=192.168.1.50:22000 remote.name=ServerSyncThing remote.client=syncthing remote.version=v2.0.0 log.pkg=model) 2025-08-13 20:00:30 INF Ignoring announced folder (folder.id=e2egz-zl49s device=WZY3IKA log.pkg=model) 2025-08-13 20:00:30 INF Established secure connection (device=WZY3IKA connection.local=192.168.1.13:40138 connection.remote=192.168.1.50:22000 connection.type=tcp-client connection.lan=true connection.crypto=TLS1.3-TLS_AES_128_GCM_SHA256 connection.prio=10 connection.id=62RBEGV3JFQLKCKJ9RTCC754IG log.pkg=connections) 2025-08-13 20:00:30 INF Additional device connection (device=WZY3IKA address=192.168.1.50:22000 count=1 log.pkg=model) 2025-08-13 20:00:30 INF Lost device connection (kind=primary device=WZY3IKA connection=192.168.1.13:22000-192.168.1.50:22000/tcp-server/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-62RBEGQHJBRH61NJ5Q7EOM69P4 error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” remaining=1 log.pkg=model) 2025-08-13 20:00:31 INF Ignoring announced folder (folder.id=e2egz-zl49s device=WZY3IKA log.pkg=model) 2025-08-13 20:00:31 INF Lost device connection (kind=primary device=WZY3IKA connection=192.168.1.13:40138-192.168.1.50:22000/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-62RBEGV3JFQLKCKJ9RTCC754IG error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” remaining=0 log.pkg=model) 2025-08-13 20:00:31 INF Connection closed (device=WZY3IKA connection=192.168.1.13:40138-192.168.1.50:22000/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-62RBEGV3JFQLKCKJ9RTCC754IG error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” log.pkg=model) 2025-08-13 20:00:31 INF Established secure connection (device=WZY3IKA connection.local=192.168.1.13:22000 connection.remote=192.168.1.50:22000 connection.type=quic-server connection.lan=true connection.crypto=TLS1.3-TLS_AES_128_GCM_SHA256 connection.prio=20 connection.id=62RBEH47J2AF6656A1VARRK9T2 log.pkg=connections) 2025-08-13 20:00:31 INF New device connection (device=WZY3IKA address=192.168.1.50:22000 remote.name=ServerSyncThing remote.client=syncthing remote.version=v2.0.0 log.pkg=model) 2025-08-13 20:00:32 INF Ignoring announced folder (folder.id=e2egz-zl49s device=WZY3IKA log.pkg=model) 2025-08-13 20:00:32 INF Lost device connection (kind=primary device=WZY3IKA connection=192.168.1.13:22000-192.168.1.50:22000/quic-server/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P20-62RBEH47J2AF6656A1VARRK9T2 error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” remaining=0 log.pkg=model) 2025-08-13 20:00:32 INF Connection closed (device=WZY3IKA connection=192.168.1.13:22000-192.168.1.50:22000/quic-server/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P20-62RBEH47J2AF6656A1VARRK9T2 error=“handling index-update for un4f9-2c79r: update (insert file): disk I/O error: read-only file system” log.pkg=model) 2025-08-13 20:00:40 INF Established secure connection (device=WZY3IKA connection.local=192.168.1.13:40144 connection.remote=192.168.1.50:22000 connection.type=tcp-client connection.lan=true connection.crypto=TLS1.3-TLS_AES_128_GCM_SHA256 connection.prio=10 connection.id=62RBEI4J6U7T2V19Q04912G7D4 log.pkg=connections) 2025-08-13 20:00:40 INF New device connection (device=WZY3IKA address=192.168.1.50:22000 remote.name=ServerSyncThing remote.client=syncthing remote.version=v2.0.0 log.pkg=model) 2025-08-13 20:00:40 INF QUIC listener shutting down (address=“[::]:22000” log.pkg=connections) 2025-08-13 20:00:41 INF TCP listener shutting down (address=“[::]:22000” log.pkg=connections) 2025-08-13 20:00:50 INF Lost device connection (kind=secondary device=WZY3IKA connection=192.168.1.13:40144-192.168.1.50:22000/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-62RBEI4J6U7T2V19Q04912G7D4 error=“Syncthing is being stopped” remaining=0 log.pkg=model) 2025-08-13 20:00:50 INF Connection closed (device=WZY3IKA connection=192.168.1.13:40144-192.168.1.50:22000/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-62RBEI4J6U7T2V19Q04912G7D4 error=“Syncthing is being stopped” log.pkg=model) 2025-08-13 20:00:50 INF Exiting (log.pkg=syncthing)

2

Hi,

Is one of the folders affected located on a path that Android presents as read-only? Which paths are used?

3

The database is apparently considered being on a read-only (broken?) filesystem

4

I am using /storage/emulated/0 and storage/6567-0800 for 2 folders.

Interesting note:

When i start android app, device shows sync (2%), doing restart of app in begging it sync some (database?) and shows more percent, after second it disconnects. Now after multiple restarting of syncthing it shows fully synced and connected normally.

I think if i do that with sd-card folder it will help. But i can keep problem for helping to investigate if need.

Upd: Problem is solved

1 Like
7

When I tried to solve the problem,
I disabled all folders (after which the connection was established)
Set up a new folder from the android application, and it synced normally.
Next, I enabled old folder, noticed that there was little progress for the first second and connection went off,
Therefore, on the status page, I turned syncthing off and on several times, gradually advancing synchronization.

After that, there were no more connection problems in versions v2.0.1, v2.0.2

I guess it’s DB problem or what else could have changed that it is working now.
I will try to compare the old (v1) and new (current v2) databases in the app. Or I can try to delete the new DB so that (i guess) it will start migration again, and we can compare v2 DB with the problem (if it will return for me) and fixed DB.

1 Like
8

Same happened to me, android 12. Until 1.3 no issues, with 2.0 and forward…slow and hard connection. It stays “slows” both connecting to windows and other android devices.

10

/me starts chanting “logs, logs, logs, …”

a3hxk1
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6 Likes
12

Yeah read-only filesystem I don’t know what to do about, but if there are other things that could be interesting. Probably most database errors will now show up as an error in the log and close the connection, while it would previously crash Syncthing instead…

1 Like
13

I’ve just tried v2.0.3 on my Nokia 7 Plus with Android 10 (but with Syncthing Tray, my own wrapper) and couldn’t reproduce the problem. I only synchronized a very small folder with just two other devices - but at least with this small setup I didn’t run into problems with the app’s data directory being read-only. It also always worked in the Android emulator (with Android 9 and 10) when I was testing the SQLite backend a while ago. So maybe something vendor specific or you’re hitting a very rare bug (in whatever part of the software stack)? Somehow I doubt the wrapper makes a difference here. I’m now also using v2.0.3 on my Android 14 phone where I have more/bigger folders/devices and also didn’t run into problems (but the more recent Android version works for you, too - so probably not really that interesting).

Interesting. When running Syncthing Tray under Android I always had problems with the service part of the app running into SIGABRT. I was pretty sure that it was caused by the Go runtime but couldn’t pin it down exactly because debugging Go runtime crashes when the runtime is embedded into a shared library loaded under Android is not easy. Interestingly, with v2/SQLite these crashes are gone as far as I can tell. This makes sense considering your statement on the database error handling and it is of course a huge change for the better. So I now officially blame leveldb for these runtime panics. (And even weirder but also in a positive sense, with v2 the stupid “Chimera” OOM killer from Samsung doesn’t like to touch the app anymore for reasons that are beyond me. So also no more SIGKILL, too.)

1 Like
15

Strange that the directory only becomes read-only at a certain size. Somehow I think there must be more to it. (I also extended my setup on the Android 10 phone a little bit and it still works. It probably still counts as “small setup”, though.)

1 Like
16

Yes, for folders at around 30gb, i had no issues, but when i tested it to about 400 gb, then it started having issues. Any way i can log the error?

17

on 2.0.7 it seems the bug is no longer there i can synca 400gb+ folder with ease

18

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