webassembly nats client over websocket

[frbrno]

Hi all,
I have written a http server which forwards a raw tcp nats connection to websocket.
The client is written in go, compiled to webassembly, running inside the browser.
I created a nats.CustomDialer and try to connect.
The result is something like this: 'nats: expected PONG, got ?PONG' error origin

So there is an unwanted symbol inside the PONG message. I added a few lines of code in func (nc *Conn) readProto()

func (nc *Conn) readProto() (string, error) {
	var (
		_buf     = [10]byte{}
		buf      = _buf[:0]
		b        = [1]byte{}
		protoEnd = byte('\n')
	)

	for {
		if n, err := nc.conn.Read(b[:1]); err != nil {
			// Do not report EOF error
			if err == io.EOF {
				return string(buf), nil
			}
			return "", err
		} else if n == 0 { //if read count is zero, dont add it to the buf
			continue
		}
		buf = append(buf, b[0])
		if b[0] == protoEnd {
			return string(buf), nil
		}
	}
}

Now i can use the nats client inside the browser and it works like a charm. I am not sure but I think this should be added to the nats client? If read length is zero, do not add it to the buffer.

[kozlovic]

Thanks, will have a look asap.

[frbrno]

nice, thanks. I think there is a reason why conn.Read returns 'n', should not be ignored. 😊

[kozlovic]

Yes, but returning 0 with err==nil is strange..

[frbrno]

yeah, I guess its related to the websocket connection. As I said, I was not sure if its worth to change nats-client code. I ll upload my code soon to github.

[frbrno]

Implementations of Read are discouraged from returning a zero byte count with a nil error, except when len(p) == 0. Callers should treat a return of 0 and nil as indicating that nothing happened; in particular it does not indicate EOF. link

it is strange...
discussion
discussion2

my playground

[derekcollison]

We are close to having our own websocket support right in the server. Will close for now but feel free to re-open.

[tupshin]

Even though this is closed, weighing my enthusiasm for implementing this here. I'm building a gui command+control app targeting wasm as one the platforms, and native websocket support would be fantastic.

[derekcollison]

We have websocket support in master, fyi. Will be in next release but is already in nightly builds.

[oderwat]

This is related to #1146 because "wasm websocket" is not "js websocket".