update udp-codec example (#1293)

tokio/Cargo.toml

@@ -88,6 +88,7 @@ tracing-core = { version = "0.1", optional = true }
 tokio-uds = { version = "0.3.0", optional = true, path = "../tokio-uds" }
 
 [dev-dependencies]
+futures-preview = "0.3.0-alpha.17"
 tokio-test = { path = "../tokio-test" }
 pin-utils = "0.1.0-alpha.4"
 env_logger = { version = "0.5", default-features = false }

tokio/examples/udp-codec.rs

@@ -0,0 +1,86 @@
+//! This example leverages `BytesCodec` to create a UDP client and server which
+//! speak a custom protocol.
+//!
+//! Here we're using the codec from `tokio-codec` to convert a UDP socket to a stream of
+//! client messages. These messages are then processed and returned back as a
+//! new message with a new destination. Overall, we then use this to construct a
+//! "ping pong" pair where two sockets are sending messages back and forth.
+
+#![feature(async_await)]
+#![deny(warnings, rust_2018_idioms)]
+
+use std::env;
+use std::error::Error;
+use std::net::SocketAddr;
+use std::time::Duration;
+
+use tokio::io;
+use tokio::net::UdpSocket;
+use tokio::util::FutureExt;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
+    let _ = env_logger::init();
+
+    let addr = env::args().nth(1).unwrap_or("127.0.0.1:0".to_string());
+    let addr = addr.parse::<SocketAddr>()?;
+
+    // Bind both our sockets and then figure out what ports we got.
+    let mut a = UdpSocket::bind(&addr)?;
+    let mut b = UdpSocket::bind(&addr)?;
+    let b_addr = b.local_addr()?;
+
+    // Start off by sending a ping from a to b, afterwards we just print out
+    // what they send us and continually send pings
+    let a = ping(&mut a, b_addr);
+
+    // The second client we have will receive the pings from `a` and then send
+    // back pongs.
+    let b = pong(&mut b);
+
+    // Run both futures simultaneously of `a` and `b` sending messages back and forth.
+    match futures::future::try_join(a, b).await {
+        Err(e) => println!("an error occured; error = {:?}", e),
+        _ => println!("done!"),
+    }
+
+    Ok(())
+}
+
+async fn ping(socket: &mut UdpSocket, b_addr: SocketAddr) -> Result<(), io::Error> {
+    socket.send_to(b"PING", &b_addr).await?;
+
+    for _ in 0..4usize {
+        let mut buffer = [0u8; 255];
+
+        let (bytes_read, addr) = socket.recv_from(&mut buffer).await?;
+
+        println!(
+            "[a] recv: {}",
+            String::from_utf8_lossy(&buffer[..bytes_read])
+        );
+
+        socket.send_to(b"PING", &addr).await?;
+    }
+
+    Ok(())
+}
+
+async fn pong(socket: &mut UdpSocket) -> Result<(), io::Error> {
+    let mut buffer = [0u8; 255];
+
+    while let Ok(Ok((bytes_read, addr))) = socket
+        .recv_from(&mut buffer)
+        .timeout(Duration::from_millis(200))
+        .await
+    {
+        println!(
+            "[b] recv: {}",
+            String::from_utf8_lossy(&buffer[..bytes_read])
+        );
+
+        socket.send_to(b"PONG", &addr).await?;
+    }
+
+    Ok(())
+}