async_rs.rs

extern crate tokio;
extern crate futures;

use futures::future;
use tokio::{net::TcpStream, prelude::Future};
use std::net::SocketAddr;

fn send(addr: SocketAddr, message: String) {
    let task = TcpStream::connect(&addr)
    .and_then(|stream| tokio::io::write_all(stream, message))
    .map_err(|e| println!("Error: {}", e))
    .map(|_| ());

    tokio::spawn(task);
}

fn main() {
    tokio::run(future::lazy(|| {
        send("8.8.8.8:1234".parse().unwrap(), String::from("46"));
        send("1.1.1.1:4321".parse().unwrap(), String::from("3"));
        Ok(())
    }));
}