SSDP or similar to detect existing distant instances

See example of SSDP in Rust here: https://github.com/johnstonskj/rust-upnp

Specifically, an example of some of the relevant fields and constants are here: https://github.com/johnstonskj/rust-upnp/blob/master/src/discovery/protocol.rs

Start by reviewing the linked rust-upnp example, especially src/discovery/protocol.rs and its SSDP fields and constants. Determine how distant instances should be discovered and what information is needed; done means existing distant instances can be detected through SSDP or a comparable discovery mechanism.

Written by the indexing model from the issue text.