// 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); } } } } }