Question

Websocket example in netty (examples) has a http request handler which:

1. performs hand shaking (at first)

2. (then) handles different types of WebSocket frames, eventually “TextWebSocketFrame”s.

There is only one url for websocket connections in this example.

The problem is, when TextWebSocketFrame based actual websocket communication starts, there is no direct way to determine websocket url from TextWebSocketFrames themselves (correct me if I am wrong).

So, how to handle different (url) websocket connections in netty?

One solution can be registering channels and their “websocket connection urls” during handshaking process.

The other is having only one websocket connection url and resolving different contexts by adding extra information to websocket messages (TextWebSocketFrames).

I don’t find these solutions elegant, so any ideas?

Answer 1

It is my understanding that when you perform a web socket handshake, it is to a specific URL. That is specified in the web socket standard. See RFC 6455. Hence, there is no URL information in the TextWebSocketFrame because the assumption is that the frame will be sent to the URL to which the socket is bound.

To handle different URLs, you will have to either:

1. Setup a different pipeline and bind to a different IP and/or port for each URL, or
2. Like you stated, customise the hand shake and store the URL with the channel.

Personally, I’ve just used JSON in a TextWebSocketFrame. In my JSON, I have a field that states the intended action. This field is used for routing to the appropriate message handler.

I think it comes down to a design decision. WebSockets are intended for long lived connections where a request message can have 0, 1 or > 1 responses. This contrasts the REST style 1 request and 1 responses model.

Hope this helps.