Sync uses various ports and protocols to function and connect peers. So depending on the network your peers are in, these shall be open and let traffic through on either side:
- Discovery of tracker and relay IPs:
HTTP, port 80 to config.usyncapp.com (via DNS name) (Sync version 2.3: http://config.usyncapp.com/sync.conf, Sync version 2.4: http://config.getsync.com/sync.conf
- Connecting to the tracker server for automatic peer discovery:
TCP and UDP, relevant port and addresses are here
- Connecting to relay server to transfer data if direct connection is not possible:
TCP and UDP, relevant port and addresses are here.
- Direct connection to transfer data:
TCP and UDP, listening port as defined in Sync Preferences.
- Peer discovery in LAN
Multicast UDP, 126.96.36.199 over port 3838
- Automatic port mapping over UPnP and NAT-PMP
UDP, multicast to 188.8.131.52 port 1900
UDP, unicast to default gateway port 5351