commands.sh

# Listen to UDP packets through port 1234
sudo tcpdump -i lo -n udp port 1234

# UDP "server"
nc -lu 127.0.0.1 1234

# UDP "client"
nc -u 127.0.0.1 1234

main.rs

// Adding relevant systems:
game_data = game_data
    .with_bundle(LaminarNetworkBundle::new(local_socket()))?
    .with_system_desc(
        SessionJoinRequestSystemDesc::default(),
        any::type_name::<SessionJoinRequestSystem>(),
        &[any::type_name::<SharedControllerInputUpdateSystem>()],
    )

fn local_socket() -> Option<LaminarSocket> {
    let local_socket_config = LaminarConfig {
        blocking_mode: false,
        ..Default::default()
    };
    let local_socket = LaminarSocket::bind_any_with_config(local_socket_config);
    match local_socket {
        Ok(local_socket) => Some(local_socket),
        Err(e) => {
            warn!("Unable to bind to local socket. Network play will be unavailable.");
            debug!("Local socket bind error: {}", e);
            None
        }
    }
}

sample_captures.sh

# from nc server
16:32:59.497639 IP 127.0.0.1.57095 > 127.0.0.1.1234: UDP, length 1

# from nc client
16:32:59.653171 IP 127.0.0.1.57095 > 127.0.0.1.1234: UDP, length 1

# from game
# [crate/network_join_play/src/system/session_join_request_system.rs:84]
# &message = "Request to join `abcd` from `azriel`"
16:33:00.965830 IP 127.0.0.1.49232 > 127.0.0.1.1234: UDP, length 52

session_join_request_system.rs

// === System that sends messages === //
let server_socket_addr =
    SocketAddr::new(session_server_config.address, session_server_config.port);

let message = format!(
    "Request to join `{}` from `{}`",
    &session_join_request_params.session_code,
    &session_join_request_params.session_device_name
);

// Connect to `server_socket_addr` and send request.
dbg!(&message);
transport_resource.send_with_requirements(
    server_socket_addr,
    message.as_bytes(),
    // None means it uses a default multiplexed stream.
    //
    // Suspect if we give it a value, the value will be a "channel" over the same
    // socket connection.
    DeliveryRequirement::ReliableOrdered(None),
    UrgencyRequirement::OnTick,
);