rust-libp2p/example/examples/echo-server.rs

// Copyright 2017 Parity Technologies (UK) Ltd.
// 
// Permission is hereby granted, free of charge, to any person obtaining a 
// copy of this software and associated documentation files (the "Software"), 
// to deal in the Software without restriction, including without limitation 
// the rights to use, copy, modify, merge, publish, distribute, sublicense, 
// and/or sell copies of the Software, and to permit persons to whom the 
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in 
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.

extern crate bytes;
extern crate futures;
extern crate libp2p_secio as secio;
extern crate libp2p_swarm as swarm;
extern crate libp2p_tcp_transport as tcp;
extern crate multiplex;
extern crate tokio_core;
extern crate tokio_io;

use futures::future::{Future, IntoFuture, loop_fn, Loop};
use futures::{Stream, Sink};
use std::env;
use swarm::{Transport, UpgradeExt, SimpleProtocol};
use tcp::TcpConfig;
use tokio_core::reactor::Core;
use tokio_io::codec::length_delimited;

fn main() {
    // Determine which address to listen to.
    let listen_addr = env::args().nth(1).unwrap_or("/ip4/0.0.0.0/tcp/10333".to_owned());

    // We start by building the tokio engine that will run all the sockets.
    let mut core = Core::new().unwrap();

    // Now let's build the transport stack.
    // We start by creating a `TcpConfig` that indicates that we want TCP/IP.
    let transport = TcpConfig::new(core.handle())

        // On top of TCP/IP, we will use either the plaintext protocol or the secio protocol,
        // depending on which one the remote supports.
        .with_upgrade({
            let plain_text = swarm::PlainTextConfig;

            let secio = {
                let private_key = include_bytes!("test-private-key.pk8");
                let public_key = include_bytes!("test-public-key.der").to_vec();
                secio::SecioConfig {
                    key: secio::SecioKeyPair::rsa_from_pkcs8(private_key, public_key).unwrap(),
                }
            };

            plain_text.or_upgrade(secio)
        })

        // On top of plaintext or secio, we will use the multiplex protocol.
        .with_upgrade(multiplex::MultiplexConfig)
        // The object returned by the call to `with_upgrade(MultiplexConfig)` can't be used as a
        // `Transport` because the output of the upgrade is not a stream but a controller for
        // muxing. We have to explicitly call `into_connection_reuse()` in order to turn this into
        // a `Transport`.
        .into_connection_reuse()

        // On top of both mutiplex and plaintext/secio, we use the "echo" protocol, which is a
        // custom protocol just for this example.
        // For this purpose, we create a `SimpleProtocol` struct.
        .with_upgrade(SimpleProtocol::new("/echo/1.0.0", |socket| {
            // This closure is called whenever a stream using the "echo" protocol has been
            // successfully negotiated. The parameter is the raw socket (implements the AsyncRead
            // and AsyncWrite traits), and the closure must return an implementation of
            // `IntoFuture` that can yield any type of object.
            Ok(length_delimited::Framed::new(socket))
        }));

    // We now have a `transport` variable that can be used either to dial nodes or listen to
    // incoming connections, and that will automatically apply all the selected protocols on top
    // of any opened stream.

    // We use it to listen on the address.
    let (listener, address) = transport
        .listen_on(swarm::Multiaddr::new(&listen_addr).expect("invalid multiaddr"))
        // If the multiaddr protocol exists but is not supported, then we get an error containing
        // the transport and the original multiaddress. Therefore we cannot directly use `unwrap()`
        // or `expect()`, but have to add a `map_err()` beforehand.
        .map_err(|(_, addr)| addr).expect("unsupported multiaddr");
    println!("Now listening on {:?}", address);

    let future = listener
        .filter_map(|(socket, client_addr)| {
            let client_addr = client_addr.to_string();

            // This closure is called whenever a new connection has been received. The `socket`
            // is a `Result<..., IoError>` which contains an error if for example protocol
            // negotiation or the secio handshake failed. We handle this situation by printing a
            // message on stderr and ignoring the connection.
            match socket {
                Ok(s) => Some((s, client_addr)),
                Err(err) => {
                    eprintln!("Failed connection attempt from {}\n => Error: {:?}",
                              client_addr, err);
                    None
                },
            }
        })

        .for_each(|(socket, client_addr)| {
            // This closure is called whenever a new connection has been received and successfully
            // upgraded to use secio/plaintext and echo.
            println!("Successfully negotiated protocol with {}", client_addr);

            // We loop forever in order to handle all the messages sent by the client.
            let client_finished = {
                let client_addr = client_addr.clone();
                loop_fn(socket, move |socket| {
                    let client_addr = client_addr.clone();
                    socket.into_future()
                        .map_err(|(err, _)| err)
                        .and_then(move |(msg, rest)| {
                            if let Some(msg) = msg {
                                // One message has been received. We send it back to the client.
                                println!("Received a message from {}: {:?}\n => Sending back \
                                          identical message to remote", client_addr, msg);
                                Box::new(rest.send(msg).map(|m| Loop::Continue(m)))
                                    as Box<Future<Item = _, Error = _>>
                            } else {
                                // End of stream. Connection closed. Breaking the loop.
                                println!("Received EOF from {}\n => Dropping connection",
                                         client_addr);
                                Box::new(Ok(Loop::Break(())).into_future())
                                    as Box<Future<Item = _, Error = _>>
                            }
                        })
                })
            };

            // We absorb errors from the `client_finished` future so that an error while processing
            // a client (eg. if the client unexpectedly disconnects) doesn't propagate and stop the
            // entire server.
            client_finished.then(move |res| {
                if let Err(err) = res {
                    println!("Error while processing client {}: {:?}", client_addr, err);
                }
                Ok(())
            })
        });

    // `future` is a future that contains all the behaviour that we want, but nothing has actually
    // started yet. Because we created the `TcpConfig` with tokio, we need to run the future
    // through the tokio core.
    core.run(future).unwrap();
}