refactor: move examples to common location

Refactor examples into separate binary crates.

Fixes https://github.com/libp2p/rust-libp2p/issues/3111.

Pull-Request: #3509.

examples/chat-example/src/main.rs

@@ -0,0 +1,153 @@
+// 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.
+
+//! A basic chat application with logs demonstrating libp2p and the gossipsub protocol
+//! combined with mDNS for the discovery of peers to gossip with.
+//!
+//! Using two terminal windows, start two instances, typing the following in each:
+//!
+//! ```sh
+//! cargo run
+//! ```
+//!
+//! Mutual mDNS discovery may take a few seconds. When each peer does discover the other
+//! it will print a message like:
+//!
+//! ```sh
+//! mDNS discovered a new peer: {peerId}
+//! ```
+//!
+//! Type a message and hit return: the message is sent and printed in the other terminal.
+//! Close with Ctrl-c.
+//!
+//! You can open more terminal windows and add more peers using the same line above.
+//!
+//! Once an additional peer is mDNS discovered it can participate in the conversation
+//! and all peers will receive messages sent from it.
+//!
+//! If a participant exits (Control-C or otherwise) the other peers will receive an mDNS expired
+//! event and remove the expired peer from the list of known peers.
+
+use async_std::io;
+use futures::{prelude::*, select};
+use libp2p::{
+    gossipsub, identity, mdns, swarm::NetworkBehaviour, swarm::SwarmEvent, PeerId, Swarm,
+};
+use std::collections::hash_map::DefaultHasher;
+use std::error::Error;
+use std::hash::{Hash, Hasher};
+use std::time::Duration;
+
+#[async_std::main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    // 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 an encrypted DNS-enabled TCP Transport over the Mplex protocol.
+    let transport = libp2p::development_transport(local_key.clone()).await?;
+
+    // We create a custom network behaviour that combines Gossipsub and Mdns.
+    #[derive(NetworkBehaviour)]
+    struct MyBehaviour {
+        gossipsub: gossipsub::Behaviour,
+        mdns: mdns::async_io::Behaviour,
+    }
+
+    // To content-address message, we can take the hash of message and use it as an ID.
+    let message_id_fn = |message: &gossipsub::Message| {
+        let mut s = DefaultHasher::new();
+        message.data.hash(&mut s);
+        gossipsub::MessageId::from(s.finish().to_string())
+    };
+
+    // Set a custom gossipsub configuration
+    let gossipsub_config = gossipsub::ConfigBuilder::default()
+        .heartbeat_interval(Duration::from_secs(10)) // This is set to aid debugging by not cluttering the log space
+        .validation_mode(gossipsub::ValidationMode::Strict) // This sets the kind of message validation. The default is Strict (enforce message signing)
+        .message_id_fn(message_id_fn) // content-address messages. No two messages of the same content will be propagated.
+        .build()
+        .expect("Valid config");
+
+    // build a gossipsub network behaviour
+    let mut gossipsub = gossipsub::Behaviour::new(
+        gossipsub::MessageAuthenticity::Signed(local_key),
+        gossipsub_config,
+    )
+    .expect("Correct configuration");
+
+    // Create a Gossipsub topic
+    let topic = gossipsub::IdentTopic::new("test-net");
+
+    // subscribes to our topic
+    gossipsub.subscribe(&topic)?;
+
+    // Create a Swarm to manage peers and events
+    let mut swarm = {
+        let mdns = mdns::async_io::Behaviour::new(mdns::Config::default(), local_peer_id)?;
+        let behaviour = MyBehaviour { gossipsub, mdns };
+        Swarm::with_async_std_executor(transport, behaviour, local_peer_id)
+    };
+
+    // 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()?)?;
+
+    println!("Enter messages via STDIN and they will be sent to connected peers using Gossipsub");
+
+    // Kick it off
+    loop {
+        select! {
+            line = stdin.select_next_some() => {
+                if let Err(e) = swarm
+                    .behaviour_mut().gossipsub
+                    .publish(topic.clone(), line.expect("Stdin not to close").as_bytes()) {
+                    println!("Publish error: {e:?}");
+                }
+            },
+            event = swarm.select_next_some() => match event {
+                SwarmEvent::Behaviour(MyBehaviourEvent::Mdns(mdns::Event::Discovered(list))) => {
+                    for (peer_id, _multiaddr) in list {
+                        println!("mDNS discovered a new peer: {peer_id}");
+                        swarm.behaviour_mut().gossipsub.add_explicit_peer(&peer_id);
+                    }
+                },
+                SwarmEvent::Behaviour(MyBehaviourEvent::Mdns(mdns::Event::Expired(list))) => {
+                    for (peer_id, _multiaddr) in list {
+                        println!("mDNS discover peer has expired: {peer_id}");
+                        swarm.behaviour_mut().gossipsub.remove_explicit_peer(&peer_id);
+                    }
+                },
+                SwarmEvent::Behaviour(MyBehaviourEvent::Gossipsub(gossipsub::Event::Message {
+                    propagation_source: peer_id,
+                    message_id: id,
+                    message,
+                })) => println!(
+                        "Got message: '{}' with id: {id} from peer: {peer_id}",
+                        String::from_utf8_lossy(&message.data),
+                    ),
+                _ => {}
+            }
+        }
+    }
+}