pub trait WebSocketHandler: Send + Sync + Sized + 'static {
    type OutboundStream: Stream<Item = Message> + Unpin + Send + Sync + 'static;

    fn connect<'life0, 'async_trait>(
        &'life0 self,
        conn: WebSocketConn
    ) -> Pin<Box<dyn Future<Output = Option<(WebSocketConn, Self::OutboundStream)>> + Send + 'async_trait>>
    where
        'life0: 'async_trait,
        Self: 'async_trait
; fn inbound<'life0, 'life1, 'async_trait>(
        &'life0 self,
        message: Message,
        conn: &'life1 mut WebSocketConn
    ) -> Pin<Box<dyn Future<Output = ()> + Send + 'async_trait>>
    where
        'life0: 'async_trait,
        'life1: 'async_trait,
        Self: 'async_trait
, { ... } fn send<'life0, 'life1, 'async_trait>(
        &'life0 self,
        message: Message,
        conn: &'life1 mut WebSocketConn
    ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'async_trait>>
    where
        'life0: 'async_trait,
        'life1: 'async_trait,
        Self: 'async_trait
, { ... } fn disconnect<'life0, 'life1, 'async_trait>(
        &'life0 self,
        conn: &'life1 mut WebSocketConn,
        close_frame: Option<CloseFrame<'static>>
    ) -> Pin<Box<dyn Future<Output = ()> + Send + 'async_trait>>
    where
        'life0: 'async_trait,
        'life1: 'async_trait,
        Self: 'async_trait
, { ... } }
Expand description

This is the trait that defines a handler for trillium websockets.

There are several mutually-exclusive ways to use this trait, and it is intended to be flexible for different use cases. If the trait does not support your use case, please open a discussion and/or build a trait on top of this trait to add additional functionality.

Simple Example

use trillium_websockets::{Message, WebSocket, WebSocketConn, WebSocketHandler};
use futures_lite::stream::{pending, Pending};

struct EchoServer;
#[trillium::async_trait]
impl WebSocketHandler for EchoServer {
    type OutboundStream = Pending<Message>; // we don't use an outbound stream in this example

    async fn connect(&self, conn: WebSocketConn) -> Option<(WebSocketConn, Self::OutboundStream)> {
        Some((conn, pending()))
    }

    async fn inbound(&self, message: Message, conn: &mut WebSocketConn) {
        let path = conn.path().to_string();
        if let Message::Text(input) = message {
            let reply = format!("received your message: {} at path {}", &input, &path);
            conn.send_string(reply).await;
        }
    }
}

let handler = WebSocket::new(EchoServer);

Using WebSocketHandler::connect only

If you have needs that are not supported by this trait, you can either pass an Fn(WebSocketConn) -> impl Future<Output=()> as a handler, or implement your own connect-only trait implementation that takes the WebSocketConn and returns None. The tcp connection will remain intact until the WebSocketConn is dropped, so you can store it in any data structure or move it between threads as needed.

Using Streams

If you define an associated OutboundStream type and return it from connect, every message in that Stream will be sent to the connected websocket client. This is useful for sending messages that are triggered by other events in the application, using whatever channel mechanism is appropriate for your application. The websocket connection will be closed if the stream ends, yielding None.

If you do not need to use streams, set OutboundStream = futures_lite::stream::Pending<Message> or a similar stream implementation that never yields. If associated type defaults were stable, we would use that.

Receiving client-sent messages

Implement WebSocketHandler::inbound to receive client-sent messages. Currently inbound messages are not represented as a stream, but this may change in the future.

Holding data inside of the implementing type

As this is a trait you implement for your own type, you can hold additional data or structs inside of your struct. There will be exactly one of these structs shared throughout the application, so async concurrency types can be used to mutate shared data.

This example holds a shared BroadcastChannel that is cloned for each OutboundStream. Any message that a connected clients sends is broadcast to every other connected client.

Importantly, this means that the dispatch and fanout of messages is managed entirely by your implementation. For an opinionated layer on top of this, see the trillium-channels crate.

use broadcaster::BroadcastChannel;
use trillium_websockets::{Message, WebSocket, WebSocketConn, WebSocketHandler};

struct EchoServer {
    channel: BroadcastChannel<Message>,
}
impl EchoServer {
    fn new() -> Self {
        Self {
            channel: BroadcastChannel::new(),
        }
    }
}

#[trillium::async_trait]
impl WebSocketHandler for EchoServer {
    type OutboundStream = BroadcastChannel<Message>;

    async fn connect(&self, conn: WebSocketConn) -> Option<(WebSocketConn, Self::OutboundStream)> {
        Some((conn, self.channel.clone()))
    }

    async fn inbound(&self, message: Message, _conn: &mut WebSocketConn) {
        if let Message::Text(input) = message {
            let message = Message::text(format!("received message: {}", &input));
            trillium::log_error!(self.channel.send(&message).await);
        }
    }
}

// fn main() {
//     trillium_smol::run(WebSocket::new(EchoServer::new()));
// }

Required Associated Types

A [Stream] type that represents Messages to be sent to this client. It is built in your implementation code, in WebSocketHandler::connect. Use Pending<Message> or another stream that never returns if you do not need to use this aspect of the trait.

Required Methods

This interface is the only mandatory function in WebSocketHandler. It receives an owned WebSocketConn and optionally returns it along with an OutboundStream type.

Provided Methods

This interface function is called once with every message received from a connected websocket client.

This interface function is called once with every outbound message in the OutboundStream. You likely do not need to implement this, but if you do, you must call conn.send(message).await or the message will not be sent.

This interface function is called with the websocket conn and, in the case of a clean disconnect, the [CloseFrame] if one is sent available.

Implementors