mdns-passive-discovery.rs

// Copyright 2018 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.

use futures::StreamExt;
use libp2p::{
    identity, mdns,
    swarm::{Swarm, SwarmEvent},
    PeerId,
};
use std::error::Error;

#[async_std::main]
async fn main() -> Result<(), Box<dyn Error>> {
    env_logger::init();

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

    // Create a transport.
    let transport = libp2p::development_transport(id_keys).await?;

    // Create an MDNS network behaviour.
    let behaviour = mdns::async_io::Behaviour::new(mdns::Config::default(), peer_id)?;

    // Create a Swarm that establishes connections through the given transport.
    // Note that the MDNS behaviour itself will not actually inititiate any connections,
    // as it only uses UDP.
    let mut swarm = Swarm::with_async_std_executor(transport, behaviour, peer_id);
    swarm.listen_on("/ip4/0.0.0.0/tcp/0".parse()?)?;

    loop {
        match swarm.select_next_some().await {
            SwarmEvent::Behaviour(mdns::Event::Discovered(peers)) => {
                for (peer, addr) in peers {
                    println!("discovered {peer} {addr}");
                }
            }
            SwarmEvent::Behaviour(mdns::Event::Expired(expired)) => {
                for (peer, addr) in expired {
                    println!("expired {peer} {addr}");
                }
            }
            _ => {}
        }
    }
}