actix-website/examples/websockets/src/main.rs

// <websockets>
use actix_web::{rt, web, App, Error, HttpRequest, HttpResponse, HttpServer};
use actix_ws::AggregatedMessage;
use futures_util::StreamExt as _;

async fn echo(req: HttpRequest, stream: web::Payload) -> Result<HttpResponse, Error> {
    let (res, mut session, stream) = actix_ws::handle(&req, stream)?;

    let mut stream = stream
        .aggregate_continuations()
        // aggregate continuation frames up to 1MiB
        .max_continuation_size(2_usize.pow(20));

    // start task but don't wait for it
    rt::spawn(async move {
        // receive messages from websocket
        while let Some(msg) = stream.next().await {
            match msg {
                Ok(AggregatedMessage::Text(text)) => {
                    // echo text message
                    session.text(text).await.unwrap();
                }

                Ok(AggregatedMessage::Binary(bin)) => {
                    // echo binary message
                    session.binary(bin).await.unwrap();
                }

                Ok(AggregatedMessage::Ping(msg)) => {
                    // respond to PING frame with PONG frame
                    session.pong(&msg).await.unwrap();
                }

                _ => {}
            }
        }
    });

    // respond immediately with response connected to WS session
    Ok(res)
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| App::new().route("/echo", web::get().to(echo)))
        .bind(("127.0.0.1", 8080))?
        .run()
        .await
}
// </websockets>

// testing requires specific headers:
// Upgrade: websocket
// Connection: Upgrade
// Sec-WebSocket-Key: SOME_KEY
// Sec-WebSocket-Version: 13