High level API for accessing getsockname() / getpeername()

There needs to be some way to get at the information in getsockname and getpeername from the high-level Stream and Listener interfaces.

It should involve an await, at least on streams, to support the PROXY protocol.

What should we do with SSLStream/SSLListener? There's a conceptual problem where the stream they're talking about doesn't exactly have an address, it's "connect to the transport's address AND THEN wrap the thing in a SSLStream". But then, it's not like getsockname/getpeername exactly has any meaning for streams anyway -- like, if you have a connected socket it's useful to be able to ask it what the two halves of the TCP 5-tuple looks like, but you can't actually do anything with this, it doesn't satisfy any invariants. Except "this might be useful for forensics".

So maybe pragmatics beats purity and SSLStream should just proxy this through to the underlying transport, and we'll leave the user to figure out how to decipher it.

Maybe a SocketAddress object that has family and sockaddr fields, plus possibly host, port, path, etc., as appropriate for the particular address?

Start by reading the high-level Stream, Listener, SSLStream, and SSLListener interfaces and tracing how they wrap transports. Investigate the existing getsockname() and getpeername() access paths, then determine the API and SocketAddress shape needed for both plain and SSL streams. Done requires an agreed design, implementation, and tests for address access and SSL behavior.