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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:
//!
//! ```sh
//! $ cargo run --example echo-udp
//! ```
//!
//! and in another terminal you can run:
//!
//! ```sh
//! $ nc -4u localhost 8080
//! ```
//!
//! Each line you type in to the `nc` terminal should be echo'd back to you!
extern crate futures;
#[macro_use]
extern crate tokio_core;
use std::{env, io};
use std::net::SocketAddr;
use futures::{Future, Poll};
use tokio_core::net::UdpSocket;
use tokio_core::reactor::Core;
struct Server {
socket: UdpSocket,
buf: Vec<u8>,
to_send: Option<(usize, SocketAddr)>,
}
impl Future for Server {
type Item = ();
type Error = io::Error;
fn poll(&mut self) -> Poll<(), io::Error> {
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 we're writable and able to do so.
if let Some((size, peer)) = self.to_send {
let amt = try_nb!(self.socket.send_to(&self.buf[..size], &peer));
println!("Echoed {}/{} bytes to {}", amt, size, peer);
self.to_send = None;
}
// If we're here then `to_send` is `None`, so we take a look for the
// next message we're going to echo back.
self.to_send = Some(try_nb!(self.socket.recv_from(&mut self.buf)));
}
}
}
fn main() {
let addr = env::args().nth(1).unwrap_or("127.0.0.1:8080".to_string());
let addr = addr.parse::<SocketAddr>().unwrap();
// Create the event loop that will drive this server, and also bind the
// socket we'll be listening to.
let mut l = Core::new().unwrap();
let handle = l.handle();
let socket = UdpSocket::bind(&addr, &handle).unwrap();
println!("Listening on: {}", addr);
// Next we'll create a future to spawn (the one we defined above) and then
// we'll run the event loop by running the future.
l.run(Server {
socket: socket,
buf: vec![0; 1024],
to_send: None,
}).unwrap();
}
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