rust-libp2p/examples/chat.rs

// Copyright 2018 Parity Technologies (UK) Ltd.
//
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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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 addresses of the first
//! instance and start the second with one of the addresses as the first argument. In the first
//! terminal window, run:
//!
//! ```sh
//! cargo run --example chat
//! ```
//!
//! It will print the PeerId and the listening addresses, 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::{
    prelude::{stream::StreamExt, *},
    select,
};
use libp2p::{
    floodsub::{self, Floodsub, FloodsubEvent},
    identity,
    mdns::{Mdns, MdnsConfig, MdnsEvent},
    swarm::SwarmEvent,
    Multiaddr, NetworkBehaviour, PeerId, Swarm,
};
use std::error::Error;

#[async_std::main]
async 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::development_transport(local_key).await?;

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

    // 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.
    // Use the derive to generate delegating NetworkBehaviour impl and require the
    // NetworkBehaviourEventProcess implementations below.
    #[derive(NetworkBehaviour)]
    #[behaviour(out_event = "OutEvent")]
    struct MyBehaviour {
        floodsub: Floodsub,
        mdns: Mdns,

        // Struct fields which do not implement NetworkBehaviour need to be ignored
        #[behaviour(ignore)]
        #[allow(dead_code)]
        ignored_member: bool,
    }

    #[derive(Debug)]
    enum OutEvent {
        Floodsub(FloodsubEvent),
        Mdns(MdnsEvent),
    }

    impl From<MdnsEvent> for OutEvent {
        fn from(v: MdnsEvent) -> Self {
            Self::Mdns(v)
        }
    }

    impl From<FloodsubEvent> for OutEvent {
        fn from(v: FloodsubEvent) -> Self {
            Self::Floodsub(v)
        }
    }

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

        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)?;
        println!("Dialed {:?}", to_dial)
    }

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

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

    // Kick it off
    loop {
        select! {
            line = stdin.select_next_some() => swarm
                .behaviour_mut()
                .floodsub
                .publish(floodsub_topic.clone(), line.expect("Stdin not to close").as_bytes()),
            event = swarm.select_next_some() => match event {
                SwarmEvent::NewListenAddr { address, .. } => {
                    println!("Listening on {:?}", address);
                }
                SwarmEvent::Behaviour(OutEvent::Floodsub(
                    FloodsubEvent::Message(message)
                )) => {
                    println!(
                        "Received: '{:?}' from {:?}",
                        String::from_utf8_lossy(&message.data),
                        message.source
                    );
                }
                SwarmEvent::Behaviour(OutEvent::Mdns(
                    MdnsEvent::Discovered(list)
                )) => {
                    for (peer, _) in list {
                        swarm
                            .behaviour_mut()
                            .floodsub
                            .add_node_to_partial_view(peer);
                    }
                }
                SwarmEvent::Behaviour(OutEvent::Mdns(MdnsEvent::Expired(
                    list
                ))) => {
                    for (peer, _) in list {
                        if !swarm.behaviour_mut().mdns.has_node(&peer) {
                            swarm
                                .behaviour_mut()
                                .floodsub
                                .remove_node_from_partial_view(&peer);
                        }
                    }
                },
                _ => {}
            }
        }
    }
}