Acknowledgements (ACKs)

When a client sends an event with a callback, the server can respond using an acknowledgement (ACK).

You can find the reference for the has_ack() and ack(...) methods in the SocketContext reference.

Detecting if the event expects an acknowledgement

if ctx.has_ack() {
    // ...
}

Responding with ack(...)

use serde::Serialize;
use sword::prelude::*;
use sword::socketio::*;

#[derive(Serialize)]
struct AckPayload {
    ok: bool,
}

#[controller(kind = Controller::SocketIo, namespace = "/chat")]
pub struct ChatController;

impl ChatController {
    #[on("ping")]
    async fn ping(&self, socket: SocketContext) {
        if socket.has_ack() {
            let _ = socket.ack(&AckPayload { ok: true });
        }
    }
}

When to use this mechanism

ACKs are useful when the client needs explicit confirmation that the server processed the event correctly or wants to receive an immediate result from the operation.