BitTorrent Sync FAQ

Actually BTSync identifies other BTSync instances in local network over port 3838 using multicast requests. So devices in local network must be visible one to another even if tracker is inaccessible. Please make sure that the port is not blocked by local firewalls.

All people who can’t sync in China over internet, please check that:
1) Your computers can resolve DNS names (tracker server) and (relay server). First would be enough for computers to “see” each other (displayed in devices tab). If they can’t be resolved – you can try to put actual IPs in your hosts file,,,
2) if you can actually connect to the tracker server. To accomplish this test you’ll need a binary file which represents a legitimate request to the tracker server, send it to tracker server and see if response comes back.
For Linux and Mac systems just get the file, put to some folder and run next command from command line:
“cat udp_req.bin | nc -u 3000”
For Windows you’ll need to download net cat utility first and run similar command:
“type udp_req.bin | nc -u 3000”
If you can reach the tracker server, you are going to get response starting with “BSYNC…” like thisxA39f1c

If you can’t – you’ll get just nothing after your command.

For the people who can’t sync in local network:
1) Please check your firewall settings, if it you are confident that nothing is blocked –
2) I would appreciate collecting full debug logs from 2 peers that can’t connect. Please provide logs for analysis and we’ll try to find out what’s happening.


If you have SyncApp issue, then we are here to help you. Having right problem description and logs will mean that your problem will be fixed in a matter of hours.

Just email us at and we will answer any question you might have.

If you will do few steps in advance, that will help us significantly. Please note, that in most cases we will need logs from both machines.

Step 0. Describe your problem

Don’t forget to describe your problem or put link to the forum post in your email.

Step 1. Turn on Debug Logging.

Windows and Mac: click on BT Sync icon in system tray and select “Enable Debug Logging”.
Linux: create file debug.txt with contents of FFFF in the .sync folder. You can find the .sync folder in the same directory where the btsync binary is located.

Step 2. Reproduce issue

Please let Sync collect logs for at least 15 minutes to get enough information.
Step 3. Attach log file to your email.

Windows: %APPDATA%\BitTorrent Sync\sync.log and sync.log.old
Mac: ~/Library/Application\ Support/BitTorrent\ Sync/sync.log and sync.log.old
Linux: ./sync/sync.log and sync.log.old


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