Multiplexed WebSocket - Application level ping/pong support

[AdamMagaluk]

"When using a fully-featured websocket client, sending a ping every now and again to keep the socket open is built-in. However, when working with plain javascript in the browser, that option is not available.

Would be it possible to allow a message along the lines of:

{type: 'keep-alive'}

or

{type: 'ping'}

And a corresponding ack response?"

Also, check the status code error that is returned when type is not valid.

[wooliet]

(Regarding the "check status code error")

The documentation for error codes says the status is 400 for bad JSON and 405 for an unknown type value.

When I send an unknown type (e.g. "ping"), I do not get the expected 405. The status returned is instead 400.

{"type":"ping"}
{"type":"error","code":400,"timestamp":1452714090158,"message":"Message validation failed."}

[AdamMagaluk]

Implemented in master, will be included in 1.0.0-beta.6