Ping事件无法发送或接收

Question

我使用ws来实现我的websocket服务器，在api文档中我发现它有一个ping / pong事件，但是，我无法收到该事件。
服务器：

wss.on("connection", function connection(ws) {
    ws.on('message', function(message) {
        console.log('received: %s', message);
    });
    ws.onclose = function () {
        console.log('client disappeared');
    };
    ws.ping('hello');//Send a ping
});

客户端：

<script>
        var ws = new WebSocket('ws://localhost:8080');

        function sendMesage() {
            ws.send('hello');
        }

        ws.onopen = function () {
            console.log('connection to server opened');
        };
        ws.onclose = function () {
            console.log('closed');
        }

        ws.onping = function () {
            console.log('ping');
        };// expect to receive ping event
    </script>