Back to My Mac
Back to My Mac was a feature introduced with Mac OS X Leopard that used Wide-Area Bonjour to securely discover services across the Internet and automatically configure ad hoc, on-demand, point-to-point encrypted connections between computers using IPsec.
Due to its generality, Back to My Mac worked for many Bonjour-enabled services, not just Screen Sharing and File Sharing. It required a router that supports either Universal Plug and Play or NAT Port Mapping Protocol. It used UDP port 4500 for point-to-point IPsec connections.
For a time, Apple included Back to My Mac in its iCloud service rather than the previously used MobileMe, thus making it free to use.
On August 9, 2018, Apple updated a support document to note that Back to My Mac would not be part of the macOS Mojave release. The support document was updated again on May 31, 2019, to indicate that Back to My Mac services would be discontinued for all other versions of macOS as of July 1, 2019.