I have installed Dropbox on 2 Ubuntu machines and enabled LAN sync. I was curious how does one Dropbox instance detect another.

  • Probably a hello, handshake, and a package. Just like your UPS driver. – surfasb Aug 18 '11 at 5:19

It looks like a UDP broadcast packet is sent over the LAN.

I found these links to support:


"we've experimented with various service discovery protocols, both standardized and our own. right now we're using UDP broadcast, but we're testing a few different ideas to see what'll work best for most people. the server is only involved in lansync negotiation to enforce our security model."


For example, if I look at a packet capture for my LAN I see "[source IP] DB-LSP-Dropbox LAN Sync Discovery Protocol" every few seconds.


It does by sending UDP packets every 30 seconds. Check the post below ...

Dropbox LAN Sync Protocol (archived)

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