rust-libp2p/examples/chat.rs

// Copyright 2018 Parity Technologies (UK) Ltd.
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//! A basic chat application demonstrating libp2p and the mDNS and floodsub protocols.
//!
//! Using two terminal windows, start two instances. If you local network allows mDNS,
//! they will automatically connect. Type a message in either terminal and hit return: the
//! message is sent and printed in the other terminal. Close with Ctrl-c.
//!
//! You can of course open more terminal windows and add more participants.
//! Dialing any of the other peers will propagate the new participant to all
//! chat members and everyone will receive all messages.
//!
//! # If they don't automatically connect
//!
//! If the nodes don't automatically connect, take note of the listening address of the first
//! instance and start the second with this address as the first argument. In the first terminal
//! window, run:
//!
//! ```sh
//! cargo run --example chat
//! ```
//!
//! It will print the PeerId and the listening address, e.g. `Listening on
//! "/ip4/0.0.0.0/tcp/24915"`
//!
//! In the second terminal window, start a new instance of the example with:
//!
//! ```sh
//! cargo run --example chat -- /ip4/127.0.0.1/tcp/24915
//! ```
//!
//! The two nodes then connect.

use async_std::{io, task};
use futures::{future, prelude::*};
use libp2p::{
    Multiaddr,
    PeerId,
    Swarm,
    NetworkBehaviour,
    identity,
    floodsub::{self, Floodsub, FloodsubEvent},
    mdns::{Mdns, MdnsEvent},
    swarm::NetworkBehaviourEventProcess
};
use std::{error::Error, task::{Context, Poll}};

fn main() -> Result<(), Box<dyn Error>> {
    env_logger::init();

    // Create a random PeerId
    let local_key = identity::Keypair::generate_ed25519();
    let local_peer_id = PeerId::from(local_key.public());
    println!("Local peer id: {:?}", local_peer_id);

    // Set up a an encrypted DNS-enabled TCP Transport over the Mplex and Yamux protocols
    let transport = libp2p::build_development_transport(local_key)?;

    // Create a Floodsub topic
    let floodsub_topic = floodsub::TopicBuilder::new("chat").build();

    // We create a custom network behaviour that combines floodsub and mDNS.
    // In the future, we want to improve libp2p to make this easier to do.
    #[derive(NetworkBehaviour)]
    struct MyBehaviour<TSubstream: AsyncRead + AsyncWrite> {
        floodsub: Floodsub<TSubstream>,
        mdns: Mdns<TSubstream>,
    }

    impl<TSubstream: AsyncRead + AsyncWrite> NetworkBehaviourEventProcess<MdnsEvent> for MyBehaviour<TSubstream> {
        fn inject_event(&mut self, event: MdnsEvent) {
            match event {
                MdnsEvent::Discovered(list) =>
                    for (peer, _) in list {
                        self.floodsub.add_node_to_partial_view(peer);
                    }
                MdnsEvent::Expired(list) =>
                    for (peer, _) in list {
                        if !self.mdns.has_node(&peer) {
                            self.floodsub.remove_node_from_partial_view(&peer);
                        }
                    }
            }
        }
    }

    impl<TSubstream: AsyncRead + AsyncWrite> NetworkBehaviourEventProcess<FloodsubEvent> for MyBehaviour<TSubstream> {
        // Called when `floodsub` produces an event.
        fn inject_event(&mut self, message: FloodsubEvent) {
            if let FloodsubEvent::Message(message) = message {
                println!("Received: '{:?}' from {:?}", String::from_utf8_lossy(&message.data), message.source);
            }
        }
    }

    // Create a Swarm to manage peers and events
    let mut swarm = {
        let mdns = task::block_on(Mdns::new())?;
        let mut behaviour = MyBehaviour {
            floodsub: Floodsub::new(local_peer_id.clone()),
            mdns
        };

        behaviour.floodsub.subscribe(floodsub_topic.clone());
        Swarm::new(transport, behaviour, local_peer_id)
    };

    // Reach out to another node if specified
    if let Some(to_dial) = std::env::args().nth(1) {
        let addr: Multiaddr = to_dial.parse()?;
        Swarm::dial_addr(&mut swarm, addr)?;
        println!("Dialed {:?}", to_dial)
    }

    // Read full lines from stdin
    let mut stdin = io::BufReader::new(io::stdin()).lines();

    // Listen on all interfaces and whatever port the OS assigns
    Swarm::listen_on(&mut swarm, "/ip4/0.0.0.0/tcp/0".parse()?)?;

    // Kick it off
    let mut listening = false;
    task::block_on(future::poll_fn(move |cx: &mut Context| {
        loop {
            match stdin.try_poll_next_unpin(cx)? {
                Poll::Ready(Some(line)) => swarm.floodsub.publish(&floodsub_topic, line.as_bytes()),
                Poll::Ready(None) => panic!("Stdin closed"),
                Poll::Pending => break
            }
        }
        loop {
            match swarm.poll_next_unpin(cx) {
                Poll::Ready(Some(event)) => println!("{:?}", event),
                Poll::Ready(None) => return Poll::Ready(Ok(())),
                Poll::Pending => {
                    if !listening {
                        if let Some(a) = Swarm::listeners(&swarm).next() {
                            println!("Listening on {:?}", a);
                            listening = true;
                        }
                    }
                    break
                }
            }
        }
        Poll::Pending
    }))
}