fn main() -> io::Result<()> {
    // load ssl keys
    let mut builder = SslAcceptor::mozilla_intermediate(SslMethod::tls()).unwrap();
    builder.set_private_key_file("./examples/key.pem", SslFiletype::PEM).unwrap();
    builder.set_certificate_chain_file("./examples/cert.pem").unwrap();
    let acceptor = builder.build();

    let num = Arc::new(AtomicUsize::new(0));

    // bind socket address and start workers. By default server uses number of
    // available logical cpu as threads count. actix net start separate
    // instances of service pipeline in each worker.
    Server::build()
        .bind(
            // configure service pipeline
            "basic", "0.0.0.0:8443",
            move || {
                let num = num.clone();
                let acceptor = acceptor.clone();

                // construct transformation pipeline
                pipeline(
                    // service for converting incoming TcpStream to a SslStream<TcpStream>
                    fn_service(move |stream: actix_rt::net::TcpStream| async move {
                        SslAcceptorExt::accept_async(&acceptor, stream.into_parts().0).await
                            .map_err(|e| println!("Openssl error: {}", e))
                    }))
                // .and_then() combinator chains result of previos service call to argument
                /// for next service calll. in this case, on success we chain
                /// ssl stream to the `logger` service.
                .and_then(fn_service(logger))
                // Next service counts number of connections
                .and_then(move |_| {
                    let num = num.fetch_add(1, Ordering::Relaxed);
                    println!("got ssl connection {:?}", num);
                    future::ok(())
                })
            },
        )?
        .run()
}