I recently had to back up one Mac to another Mac using rsync (which runs on top of SSH) and I discovered that you can't simply rsync / ssh from one Mac to another. And, yes, I know that this change happened years and years ago but I don't often go Mac to Mac (using I go Mac to Linux Server).
Here's the trick:
- Make sure your Macs are both on the same wifi access point or ethernet network
- Go into System Preferences
- Go into Sharing
- Turn on Remote Login
I'd also recommend that you Turn on File Sharing also but think about that a bit before you do so.