// You can run this example from the root of the mio repo:
// cargo run --example udp_server --features="os-poll udp"
use log::warn;
use mio::net::UdpSocket;
use mio::{Events, Interest, Poll, Token};
use std::io;
// A token to allow us to identify which event is for the `UdpSocket`.
const UDP_SOCKET: Token = Token(0);
fn main() -> io::Result<()> {
env_logger::init();
// Create a poll instance.
let mut poll = Poll::new()?;
// Create storage for events. Since we will only register a single socket, a
// capacity of 1 will do.
let mut events = Events::with_capacity(1);
// Setup the UDP socket.
let addr = "127.0.0.1:9000".parse().unwrap();
let mut socket = UdpSocket::bind(addr)?;
// Register our socket with the token defined above and an interest in being
// `READABLE`.
poll.registry()
.register(&mut socket, UDP_SOCKET, Interest::READABLE)?;
println!("You can connect to the server using `nc`:");
println!(" $ nc -u 127.0.0.1 9000");
println!("Anything you type will be echoed back to you.");
// Initialize a buffer for the UDP packet. We use the maximum size of a UDP
// packet, which is the maximum value of 16 a bit integer.
let mut buf = [0; 1 << 16];
// Our event loop.
loop {
// Poll to check if we have events waiting for us.
poll.poll(&mut events, None)?;
// Process each event.
for event in events.iter() {
// Validate the token we registered our socket with,
// in this example it will only ever be one but we
// make sure it's valid none the less.
match event.token() {
UDP_SOCKET => loop {
// In this loop we receive all packets queued for the socket.
match socket.recv_from(&mut buf) {
Ok((packet_size, source_address)) => {
// Echo the data.
socket.send_to(&buf[..packet_size], source_address)?;
}
Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
// If we get a `WouldBlock` error we know our socket
// has no more packets queued, so we can return to
// polling and wait for some more.
break;
}
Err(e) => {
// If it was any other kind of error, something went
// wrong and we terminate with an error.
return Err(e);
}
}
},
_ => {
// This should never happen as we only registered our
// `UdpSocket` using the `UDP_SOCKET` token, but if it ever
// does we'll log it.
warn!("Got event for unexpected token: {:?}", event);
}
}
}
}
}