Instead, we're layering platform-specific code in external libraries. At the raw C-level bindings, we have libc [2] and winapi [3]. For higher level APIs, we've got Mio [4] which abstracts the system APIs, and now Tokio [5], which uses futures to simplify async operations.
We're just working our way up the stack. All of these are being developed by members of the various Rust teams, so they're as "official" as everything else we're doing.
[1]: https://doc.rust-lang.org/std/net/ [2]: https://crates.io/crates/libc [3]: https://crates.io/crates/winapi [4]: https://github.com/carllerche/mio [5]: https://tokio.rs/
Thread-per-connection is the simplest way to do concurrent networking in Rust using only libstd, but it's not the way that most Rust programmers would actually use (at least, not for a production server handling a large number of connections).