/**
* Receives a Ping message.
*
* <p>A Ping message may be sent or received by either client or server. It may serve either as
* a keepalive or as a means to verify that the remote endpoint is still responsive.
*
* <p>The message will consist of not more than {@code 125} bytes: {@code message.remaining() <=
* 125}.
*
* <p>The {@code onPing} is invoked zero or more times in between {@code onOpen} and ({@code
* onClose} or {@code onError}).
*
* <p>If an exception is thrown from this method or the returned {@code CompletionStage}
* completes exceptionally, then {@link #onError(WebSocket, Throwable) onError} will be invoked
* with this exception.
*
* @implNote
* <p>Replies with a Pong message and requests one more message when the Pong has been sent.
* @param webSocket the WebSocket
* @param message the message
* @return a CompletionStage that completes when the message processing is done; or {@code null}
* if already done
*/
default CompletionStage<?> onPing(WebSocket webSocket, ByteBuffer message) {
return webSocket.sendPong(message).thenRun(() -> webSocket.request(1));
}
