Add the proxy example from #100

examples/proxy.rs

@@ -0,0 +1,112 @@
+//! A proxy that forwards data to another server and forwards that server's
+//! responses back to clients.
+
+extern crate futures;
+extern crate tokio_core;
+extern crate tokio_io;
+
+use std::sync::Arc;
+use std::env;
+use std::net::{Shutdown, SocketAddr};
+use std::io::{self, Read, Write};
+
+use futures::stream::Stream;
+use futures::{Future, Poll};
+use tokio_core::net::{TcpListener, TcpStream};
+use tokio_core::reactor::Core;
+use tokio_io::{AsyncRead, AsyncWrite};
+use tokio_io::io::{copy, shutdown};
+
+fn main() {
+    let listen_addr = env::args().nth(1).unwrap_or("127.0.0.1:8081".to_string());
+    let listen_addr = listen_addr.parse::<SocketAddr>().unwrap();
+
+    let server_addr = env::args().nth(2).unwrap_or("127.0.0.1:8080".to_string());
+    let server_addr = server_addr.parse::<SocketAddr>().unwrap();
+
+    // Create the event loop that will drive this server.
+    let mut l = Core::new().unwrap();
+    let handle = l.handle();
+
+    // Create a TCP listener which will listen for incoming connections.
+    let socket = TcpListener::bind(&listen_addr, &l.handle()).unwrap();
+    println!("Listening on: {}", listen_addr);
+    println!("Proxying to: {}", server_addr);
+
+    let done = socket.incoming().for_each(move |(client, client_addr)| {
+        let server = TcpStream::connect(&server_addr, &handle);
+        let amounts = server.and_then(move |server| {
+            // Create separate read/write handles for the TCP clients that we're
+            // proxying data between. Note that typically you'd use
+            // `AsyncRead::split` for this operation, but we want our writer
+            // handles to have a custom implementation of `shutdown` which
+            // actually calls `TcpStream::shutdown` to ensure that EOF is
+            // transmitted properly across the proxied connection.
+            //
+            // As a result, we wrap up our client/server manually in arcs and
+            // use the impls below on our custom `MyTcpStream` type.
+            let client_reader = MyTcpStream(Arc::new(client));
+            let client_writer = client_reader.clone();
+            let server_reader = MyTcpStream(Arc::new(server));
+            let server_writer = server_reader.clone();
+
+            // Copy the data (in parallel) between the client and the server.
+            // After the copy is done we indicate to the remote side that we've
+            // finished by shutting down the connection.
+            let client_to_server = copy(client_reader, server_writer)
+                .and_then(|(n, _, server_writer)| {
+                    shutdown(server_writer).map(move |_| n)
+                });
+
+            let server_to_client = copy(server_reader, client_writer)
+                .and_then(|(n, _, client_writer)| {
+                    shutdown(client_writer).map(move |_| n)
+                });
+
+            client_to_server.join(server_to_client)
+        });
+
+        let msg = amounts.map(move |(from_client, from_server)| {
+            println!("client at {} wrote {} bytes and received {} bytes",
+                     client_addr, from_client, from_server);
+        }).map_err(|e| {
+            // Don't panic. Maybe the client just disconnected too soon.
+            println!("error: {}", e);
+        });
+        handle.spawn(msg);
+
+        Ok(())
+    });
+    l.run(done).unwrap();
+}
+
+// This is a custom type used to have a custom implementation of the
+// `AsyncWrite::shutdown` method which actually calls `TcpStream::shutdown` to
+// notify the remote end that we're done writing.
+#[derive(Clone)]
+struct MyTcpStream(Arc<TcpStream>);
+
+impl Read for MyTcpStream {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        (&*self.0).read(buf)
+    }
+}
+
+impl Write for MyTcpStream {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        (&*self.0).write(buf)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl AsyncRead for MyTcpStream {}
+
+impl AsyncWrite for MyTcpStream {
+    fn shutdown(&mut self) -> Poll<(), io::Error> {
+        try!(self.0.shutdown(Shutdown::Write));
+        Ok(().into())
+    }
+}