NextCloud synchronisation mechanics - WOL compliant maybe?

In trying to find more details about the way file syncing works, I fired up wireshark to test a small set-up being:

  • Client 1 (192.168.1.16)
  • Client 2 (192.168.1.11)
  • Nextcloud Server (192.168.1.201)

Client 1 saved a 10kb txt file on the server, server synced the file on Client 2 in a span of 33 seconds.

I could see the entire TCP negotiation exchange between the NextCloud Server and Client 2, but for some strange reason, I could not capture TCP packets between Client 1 and the server apart from NBNS packets from Client 1 sent to the entire network (ARP).

Here is the image of the captured data exchanged between Client 2 and the Server.

p.s. the connection to the server is secured via 443.

I am of the opinion that the syncing happens over background flagging systems…

Any help on this please