Простые приложения на Rust — Как запустить

use std::io::{Read, Write};
use std::net::{TcpListener, TcpStream};

fn handle(mut stream: TcpStream) -> std::io::Result<()> {
    let mut buf = [0u8; 1024];
    let n = stream.read(&mut buf)?;
    let req = String::from_utf8_lossy(&buf[..n]);
    let body = r#"{"ok":true}"#;
    let response = format!(
        "HTTP/1.1 200 OK\r\nContent-Type: application/json\r\nContent-Length: {}\r\n\r\n{}",
        body.len(),
        body
    );
    stream.write_all(response.as_bytes())
}

fn main() -> std::io::Result<()> {
    let listener = TcpListener::bind("127.0.0.1:3000")?;
    for stream in listener.incoming().flatten() {
        let _ = handle(stream);
    }
    Ok(())
}