How to build multiple concurrent servers with Rust and Tokio?

Question

I'm looking to build multiple concurrent servers on different ports with Rust and Tokio:

let mut core = Core::new().unwrap();
let handle = core.handle();

// I want to bind to multiple port here if it's possible with simple addresses
let addr = "127.0.0.1:80".parse().unwrap();
let addr2 = "127.0.0.1:443".parse().unwrap();

// Or here if there is a special function on the TcpListener
let sock = TcpListener::bind(&addr, &handle).unwrap();

// Or here if there is a special function on the sock
let server = sock.incoming().for_each(|(client_stream, remote_addr)| {
    // And then retrieve the current port in the callback
    println!("Receive connection on {}!", mysterious_function_to_retrieve_the_port);
    Ok(())
});

core.run(server).unwrap();

Is there an option with Tokio to listen to multiple ports or do I need to create a simple thread for each port and run Core::new() in each?

Thanks to rust-scoped-pool, I have:

let pool = Pool::new(2);

let mut listening_on = ["127.0.0.1:80", "127.0.0.1:443"];

pool.scoped(|scope| {
    for address in &mut listening_on {
        scope.execute(move ||{
            let mut core = Core::new().unwrap();
            let handle = core.handle();

            let addr = address.parse().unwrap();
            let sock = TcpListener::bind(&addr, &handle).unwrap();

            let server = sock.incoming().for_each(|(client_stream, remote_addr)| {
                println!("Receive connection on {}!", address);
                Ok(())
            });

            core.run(server).unwrap();
        });
    }
});

rust-scoped-pool is the only solution I have found to execute multiple threads and wait forever after spawning them. I think it's working but I was wondering if a simpler solution existed.

Answer 1

You can run multiple servers from one thread. core.run(server).unwrap(); is just a convenience method and not the only/main way to do things.

Instead of running the single ForEach to completion, spawn each individually and then just keep the thread alive:

let mut core = Core::new().unwrap();
let handle = core.handle();

// I want to bind to multiple port here if it's possible with simple addresses
let addr = "127.0.0.1:80".parse().unwrap();
let addr2 = "127.0.0.1:443".parse().unwrap();

// Or here if there is a special function on the TcpListener
let sock = TcpListener::bind(&addr, &handle).unwrap();

// Or here if there is a special function on the sock
let server = sock.incoming().for_each(|(client_stream, remote_addr)| {
    // And then retrieve the current port in the callback
    println!("Receive connection on {}!", mysterious_function_to_retrieve_the_port);
    Ok(())
});

handle.spawn(sock);
handle.spawn(server);

loop {
    core.turn(None);
}

Answer 2

I'd just like to follow up that there seems to be a slightly less manual way to do things than 46bit's answer (at least as of 2019).

let addr1 = "127.0.0.1:80".parse().unwrap();
let addr2 = "127.0.0.1:443".parse().unwrap();

let sock1 = TcpListener::bind(&addr1, &handle).unwrap();
let sock2 = TcpListener::bind(&addr2, &handle).unwrap();

let server1 = sock1.incoming().for_each(|_| Ok(()));
let server2 = sock2.incoming().for_each(|_| Ok(()));

let mut runtime = tokio::runtime::Runtime()::new().unwrap();

runtime.spawn(server1);
runtime.spawn(server2);

runtime.shutdown_on_idle().wait().unwrap();