Well, I found this slightly unintuitive. If you want rsync to use a specific non-standard port, and you don't have the rsync daemon running, you need to force ssh to use this port, like so:
rsync -ar --partial --progress --rsh='ssh -p 12345' username@xyz.abc.com:/path/to/your/files .
(or you are going to get errors referring to port 22 despite your best efforts to avoid this port with --port=12345 or similar attempts at the appropriate argument which rsync does not actually support).