rust-libp2p/examples/mdns-passive-discovery.rs

// Copyright 2018 Parity Technologies (UK) Ltd.
//
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use async_std::task;
use libp2p::mdns::service::{MdnsPacket, MdnsService};
use std::error::Error;

fn main() -> Result<(), Box<dyn Error>> {
    // This example provides passive discovery of the libp2p nodes on the
    // network that send mDNS queries and answers.
    task::block_on(async move {
        let mut service = MdnsService::new().await?;
        loop {
            let (srv, packet) = service.next().await;
            match packet {
                MdnsPacket::Query(query) => {
                    // We detected a libp2p mDNS query on the network. In a real application, you
                    // probably want to answer this query by doing `query.respond(...)`.
                    println!("Detected query from {:?}", query.remote_addr());
                }
                MdnsPacket::Response(response) => {
                    // We detected a libp2p mDNS response on the network. Responses are for
                    // everyone and not just for the requester, which makes it possible to
                    // passively listen.
                    for peer in response.discovered_peers() {
                        println!("Discovered peer {:?}", peer.id());
                        // These are the self-reported addresses of the peer we just discovered.
                        for addr in peer.addresses() {
                            println!(" Address = {:?}", addr);
                        }
                    }
                }
                MdnsPacket::ServiceDiscovery(query) => {
                    // The last possibility is a service detection query from DNS-SD.
                    // Just like `Query`, in a real application you probably want to call
                    // `query.respond`.
                    println!("Detected service query from {:?}", query.remote_addr());
                }
            }
            service = srv
        }
    })
}