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/ping-example/src/main.rs

@@ -0,0 +1,90 @@
+// 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.
+
+//! Ping example
+//!
+//! See ../src/tutorial.rs for a step-by-step guide building the example below.
+//!
+//! In the first terminal window, run:
+//!
+//! ```sh
+//! cargo run
+//! ```
+//!
+//! 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 -- /ip4/127.0.0.1/tcp/24915
+//! ```
+//!
+//! The two nodes establish a connection, negotiate the ping protocol
+//! and begin pinging each other.
+
+use futures::prelude::*;
+use libp2p::{
+    identity, ping,
+    swarm::{keep_alive, NetworkBehaviour, Swarm, SwarmEvent},
+    Multiaddr, PeerId,
+};
+use std::error::Error;
+
+#[async_std::main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    let local_key = identity::Keypair::generate_ed25519();
+    let local_peer_id = PeerId::from(local_key.public());
+    println!("Local peer id: {local_peer_id:?}");
+
+    let transport = libp2p::development_transport(local_key).await?;
+
+    let mut swarm = Swarm::with_async_std_executor(transport, Behaviour::default(), local_peer_id);
+
+    // Tell the swarm to listen on all interfaces and a random, OS-assigned
+    // port.
+    swarm.listen_on("/ip4/0.0.0.0/tcp/0".parse()?)?;
+
+    // Dial the peer identified by the multi-address given as the second
+    // command-line argument, if any.
+    if let Some(addr) = std::env::args().nth(1) {
+        let remote: Multiaddr = addr.parse()?;
+        swarm.dial(remote)?;
+        println!("Dialed {addr}")
+    }
+
+    loop {
+        match swarm.select_next_some().await {
+            SwarmEvent::NewListenAddr { address, .. } => println!("Listening on {address:?}"),
+            SwarmEvent::Behaviour(event) => println!("{event:?}"),
+            _ => {}
+        }
+    }
+}
+
+/// Our network behaviour.
+///
+/// For illustrative purposes, this includes the [`KeepAlive`](keep_alive::Behaviour) behaviour so a continuous sequence of
+/// pings can be observed.
+#[derive(NetworkBehaviour, Default)]
+struct Behaviour {
+    keep_alive: keep_alive::Behaviour,
+    ping: ping::Behaviour,
+}