WebSocket-over-HTTP doesn't respond to standalone PING when structured according to the standard example

[harmony7]

When WebSocket-over-HTTP is used according to the standard example, it doesn't handle standalone PING.

This is because of the loop it uses:

        while (wsContext.canRecv()) {
            const message = wsContext.recv();

            if (message == null) {
                // If return value is undefined then connection is closed
                wsContext.close();
                break;
            }

            // Handle the message...
        }

Within wsContext.recv(), js-grip automatically handles PING by writing an outgoing PONG.
However, the ws.Context.canRecv() function only returns true in response to the messages: ['TEXT', 'BINARY', 'CLOSE', 'DISCONNECT'].

Therefore, if the only message in the queue is 'PING', it is never reaches recv().