Add UDP echo server example.

examples/echo-udp.rs

@@ -0,0 +1,75 @@
+//! An UDP echo server that just sends back everything that it receives.
+
+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;
+
+/// UDP echo server
+struct Server {
+    socket : UdpSocket,
+    buf : Vec<u8>,
+    to_send : Option<(usize, SocketAddr)>,
+}
+
+impl Server {
+    fn new(s : UdpSocket) -> Self {
+        Server {
+            socket: s,
+            to_send: None,
+            buf: vec![0u8; 1600],
+        }
+    }
+}
+
+impl Future for Server {
+    type Item = ();
+    type Error = io::Error;
+
+    fn poll(&mut self) -> Poll<(), io::Error> {
+        loop {
+            if let Some((size, peer)) = self.to_send.take() {
+                match self.socket.send_to(&self.buf[..size], &peer) {
+                    Err(e) => {
+                        self.to_send = Some((size, peer));
+                        return try_nb!(Err(e));
+                    },
+                    Ok(_) => {
+                        println!("Echoed {} bytes", size);
+                    }
+                }
+            }
+
+            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
+    let mut l = Core::new().unwrap();
+    let handle = l.handle();
+
+    // Create and bind an UDP socket
+    let socket = UdpSocket::bind(&addr, &handle).unwrap();
+
+    // Inform that we have are listening
+    println!("Listening on: {}", addr);
+
+    // Create a server future
+    let server = Server::new(socket);
+
+    // Start event loop with the initial future: UDP echo server
+    l.run(server).unwrap();
+}