websocket-rs 0.1.4

Designed for [HAWK](https://github.com/euvoor/hawk)

Example
=======

```rust
use tokio::net::TcpListener;

use http_rs::Http;
use websocket_rs::{ Websocket, Opcode };

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut listener = TcpListener::bind("127.0.0.1:8080").await?;

    println!("Listening for websocket connections on 127.0.0.1:8080");

    while let Ok((stream, addr)) = listener.accept().await {
        tokio::spawn(async move {
            println!("New connection from {:?}", addr);

            let mut http = Http::new(stream);

            if let Some(req) = http.next().await {
                if req.for_websocket() {
                    let mut ws = Websocket::new_with_key(
                        http.transport.into_inner(),
                        req.headers.get("sec-websocket-key").unwrap().to_string()
                    );

                    while let Some(msg) = ws.next().await {
                        println!("{:?}", msg);

                        if msg.opcode == Opcode::Text {
                            let response = format!("Received: {:?}", msg.payload);
                            ws.send_text(response).await.unwrap();
                        }
                    }

                    println!("Client from {:?} disconnected", addr);
                }
            }
        });
    }

    Ok(())
}
```

TODO
====
- [*] Handle errors properly
- [x] Receive opcode TEXT
- [x] Pong when Ping is received
- [x] Handle all payload lengths (**le 125**, **=126**, **=127**)
- [x] Mask key
- [x] Close websocket connection
- [x] Read fragmented frames
- [x] Extract websocket to its own crate
- [ ] Add binary support
- [ ] Send fragmented frames when the size reaches a treshold
- [ ] Schedule ping/pong
- [ ] Pong with application data included in ping
- [ ] Keep track of connected clients