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//! An UDP echo server that just sends back everything that it receives.
//!
//! If you're on Unix you can test this out by in one terminal executing:
//!
//! cargo run --example echo-udp
//!
//! and in another terminal you can run:
//!
//! cargo run --example connect -- --udp 127.0.0.1:8080
//!
//! Each line you type in to the `nc` terminal should be echo'd back to you!
#![warn(rust_2018_idioms)]
use std::error::Error;
use std::net::SocketAddr;
use std::{env, io};
use tokio::net::UdpSocket;
struct Server {
socket: UdpSocket,
buf: Vec<u8>,
to_send: Option<(usize, SocketAddr)>,
}
impl Server {
async fn run(self) -> Result<(), io::Error> {
let Server {
socket,
mut buf,
mut to_send,
} = self;
loop {
// First we check to see if there's a message we need to echo back.
// If so then we try to send it back to the original source, waiting
// until it's writable and we're able to do so.
if let Some((size, peer)) = to_send {
let amt = socket.send_to(&buf[..size], &peer).await?;
println!("Echoed {}/{} bytes to {}", amt, size, peer);
}
// If we're here then `to_send` is `None`, so we take a look for the
// next message we're going to echo back.
to_send = Some(socket.recv_from(&mut buf).await?);
}
}
}
#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
let addr = env::args()
.nth(1)
.unwrap_or_else(|| "127.0.0.1:8080".to_string());
let socket = UdpSocket::bind(&addr).await?;
println!("Listening on: {}", socket.local_addr()?);
let server = Server {
socket,
buf: vec![0; 1024],
to_send: None,
};
// This starts the server task.
server.run().await?;
Ok(())
}
|
