use std::env;
use std::net::{TcpListener, TcpStream};

fn handle_client(stream: TcpStream) {
    println!("---> handling stream {:?}", stream);
    // ...
}

fn main() -> std::io::Result<()> {
    let mut addr = String::from("127.0.0.1:19721");
    if let Ok(v) = env::var("ADDR") {
        addr = String::from(v.as_str());
    }

    println!("listening at {}", addr);
    let listener = TcpListener::bind(addr)?;

    for stream in listener.incoming() {
        handle_client(stream?);
    }
    Ok(())
}