tokio-rs/tokio ? reverse-engineered prompt

I want to build a core library in Rust for writing high-performance, asynchronous networking applications. It should be a foundational toolkit, kind of like a runtime, for building fast and reliable servers that can handle a ton of simultaneous connections without blocking.

The main features should be an efficient task scheduler, tools for asynchronous TCP and UDP sockets, and basic timers. The goal is to create an event-driven platform that takes advantage of Rust's safety and performance to build scalable network services. This isn't a final application itself, but the engine that powers them.

Please include a simple example to show how it works, like a basic TCP echo server that listens on a port and sends back whatever data it receives from a client. That would be a perfect demonstration of its capabilities.