Add WAMP to the list of allowed websocket subprotocols.

[blopker]

This request allows libraries like https://github.com/blopker/WAMPlay to use AutobahnJS for websocket RPC/PubSub.

Originally the subprotocol list was null. This tells Netty to reject any header with the "Sec-WebSocket-Protocol" field set. Setting the string to "wamp" allows AutobahnJS to connect to Play without using ugly workarounds. To add further protocols (though I'm not aware of others) just set the string to "wamp,otherprotocol".

[blopker]

Also, I already signed the CLA.

[cloudbees-pull-request-builder]

play2-master-PRs #128 SUCCESS
This pull request looks good

[nraychaudhuri]

@jroper what do you think?

[jroper]

If it's changed to load the CSV list from configuration, then I think it's ok. But I don't want just one subprotocol hard coded in Play.

[jroper]

The configuration key should be something like http.netty.websocket.subprotocols.

[nraychaudhuri]

Good idea.

[blopker]

Where should I add the http.netty.websocket.subprotocols key? I'm not very familiar with Scala.

Once I set the key I imagine I'll put something like Option(System.getProperty("http.netty.websocket.subprotocols")).orElse(null) Right?

[jroper]

No, it should come from the Play application.conf configuration file, which is accessible through the play Application object. You can pass this through to this method from PlayDefaultUpstreamHandler, which has a reference to Application.