Devices remain disconnected, need help debugging.

I use an Android device (syncthing-android) and a macOS device (syncthing-macos). For a month, the devices synchronized files without a problem but now they always remain disconnected. The issue persists even after restarting Syncthing on each device. It seems they can’t see each other on my home network.

If it’s relevant, more information about my setup:

  • Both devices are set to synchronize over 8,000 files, many of which frequently update.
  • Both devices frequently run out of storage space. The issue persists even after freeing space.
  • The Android device is disconnected from any network for long periods, but mainly uses my home network.

Unfortunately the logs on both devices don’t show any apparent errors.

Feel free to ask questions about my setup or suggest solutions. Does anyone know what I can do to debug, so I can file a bug report?

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Please post screenshots showing the Web GUI on both devices. On Android, you can open it from the left sliding menu. Be sure to unfold the relevant remote device on each side before taking the screenshots.

Also, you said the logs didn’t show any errors. If possible, you may as well share upload the logs too (from both devices).

Other than that, I assume you’ve already checked the obvious stuff like a firewall possibly blocking direct connections, etc.

Awkward… On macOS, I disabled the firewall (which blocked all incoming connections) and both devices instantly connected. My apologies for not fully troubleshooting.

However before the issue occurred, the two devices connected and synchronized (lots of) data while the macOS firewall was enabled. They were able to connect through the firewall for a few weeks. I’m not sure how that worked if I blocked incoming connections.

Here’s the syncthing-macos log from right after the firewall was disabled, for what it’s worth.

I [redacted] device identifiers, directory paths, and network addresses that I didn’t feel comfortable sharing. I can describe the missing information on request.

2021-11-01 23:32:55 My ID: [redacted]
2021-11-01 23:32:56 Single thread SHA256 performance is 173 MB/s using crypto/sha256 (135 MB/s using minio/sha256-simd).
2021-11-01 23:32:56 Hashing performance is 139.05 MB/s
2021-11-01 23:32:56 Overall send rate is unlimited, receive rate is unlimited
2021-11-01 23:32:56 Using discovery mechanism: IPv4 local broadcast discovery on port 21027
2021-11-01 23:32:56 Using discovery mechanism: IPv6 local multicast discovery on address [redacted]
2021-11-01 23:32:56 TCP listener ([::]:22000) starting
2021-11-01 23:32:56 Relay listener (dynamic+https://relays.syncthing.net/endpoint) starting
2021-11-01 23:32:56 QUIC listener ([::]:22000) starting
2021-11-01 23:32:57 quic://0.0.0.0:22000 detected NAT type: Full cone NAT
2021-11-01 23:32:57 ...
2021-11-01 23:32:57 quic://0.0.0.0:22000 resolved external address quic://[redacted] (via stun.syncthing.net:3478)
2021-11-01 23:32:57 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:32:57 Established secure connection to [redacted] at [redacted]-[redacted]/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2021-11-01 23:32:57 Device [redacted] client is "syncthing v1.18.2" named "" at [redacted]-[redacted]/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2021-11-01 23:32:59 GUI and API listening on 127.0.0.1:8384
2021-11-01 23:32:59 Access the GUI via the following URL: https://127.0.0.1:8384/
2021-11-01 23:32:59 My name is ""
2021-11-01 23:32:59 Device [redacted] is "" at [dynamic]
2021-11-01 23:32:59 Ready to synchronize "[redacted]" ([redacted]) (sendreceive)
2021-11-01 23:33:00 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:00 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:00 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:00 Connection to [redacted] at [redacted]-[redacted]/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256 closed: reading length: read tcp [redacted]->[redacted]: read: connection reset by peer
2021-11-01 23:33:00 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:00 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:01 Ready to synchronize "[redacted]/" ([redacted]) (receiveonly)
2021-11-01 23:33:01 Established secure connection to [redacted] at [redacted]-[redacted]/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2021-11-01 23:33:01 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:01 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:01 Device [redacted] client is "syncthing v1.18.2" named "" at [redacted]-[redacted]/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2021-11-01 23:33:01 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:02 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:02 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:02 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:02 Ready to synchronize "[redacted]" ([redacted]) (receiveonly)
2021-11-01 23:33:03 Ready to synchronize "[redacted]" ([redacted]) (sendreceive)
2021-11-01 23:33:03 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:03 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:06 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:06 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:07 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:07 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:08 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:08 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:08 Completed initial scan of receiveonly folder "[redacted]/" ([redacted])
2021-11-01 23:33:09 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:33:12 Detected 1 NAT service
2021-11-01 23:33:57 Joined relay relay://[redacted]
2021-11-01 23:34:09 Connection to [redacted] at [redacted]-[redacted]/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256 closed: writing message: write tcp [redacted]->[redacted]: write: broken pipe
2021-11-01 23:34:15 Puller (folder "[redacted]" ([redacted]), item "[redacted]"): syncing: no connected device has the required version of this file
2021-11-01 23:34:15 Puller (folder "[redacted]" ([redacted]), item "[redacted]"): syncing: no connected device has the required version of this file
2021-11-01 23:34:15 "[redacted]" ([redacted]): Failed to sync 2 items
2021-11-01 23:34:15 Folder "[redacted]" ([redacted]) isn't making sync progress - retrying in 2m5s.
2021-11-01 23:34:18 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:34:18 Puller (folder "[redacted]" ([redacted]), item "[redacted]"): syncing: no connected device has the required version of this file
2021-11-01 23:34:18 Puller (folder "[redacted]" ([redacted]), item "[redacted]"): syncing: no connected device has the required version of this file
2021-11-01 23:34:18 "[redacted]" ([redacted]): Failed to sync 2 items
2021-11-01 23:34:18 Folder "[redacted]" ([redacted]) isn't making sync progress - retrying in 1m0s.
2021-11-01 23:35:05 Established secure connection to [redacted] at [redacted]:22000-[redacted]:22000/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2021-11-01 23:35:05 Device [redacted] client is "syncthing v1.18.2" named "" at [redacted]:22000-[redacted]:22000/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2021-11-01 23:35:31 Completed initial scan of receiveonly folder "[redacted]" ([redacted])
2021-11-01 23:36:15 quic://0.0.0.0:22000 resolved external address quic://[redacted] (via stun.syncthing.net:3478)
2021-11-01 23:36:50 Joined relay relay://[redacted]
2021-11-01 23:37:25 Completed initial scan of sendreceive folder "[redacted]" ([redacted])
2021-11-01 23:38:31 Device [redacted] folder "[redacted]" ([redacted]) has a new index ID ([redacted])
2021-11-01 23:39:03 Device [redacted] folder "[redacted]" ([redacted]) has a new index ID ([redacted])
2021-11-01 23:39:17 Completed initial scan of sendreceive folder "[redacted]" ([redacted])
2021-11-01 23:41:01 Reverting folder [redacted]
2021-11-01 23:41:02 Revert: deleting ._.DS_Store: removing item to be replaced: remove [redacted]._.DS_Store: no such file or directory
2021-11-01 23:43:23 Connection to [redacted] at [redacted]-[redacted]:22000/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256 closed: writing message: write tcp [redacted]->[redacted]:22000: write: broken pipe

My issue is resolved. 🤦 I re-enabled the firewall with an exception for Syncthing’s incoming connections.

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