如何处理Netty 4中的PING/PONG帧？

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.*;

public class PingPongHandler extends SimpleChannelInboundHandler<WebSocketFrame> {

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, WebSocketFrame frame) throws Exception {
        if (frame instanceof PingWebSocketFrame) {
            // 接收到PING帧
            System.out.println("Received PING frame");

            // 发送PONG帧作为响应
            ctx.channel().writeAndFlush(new PongWebSocketFrame(Unpooled.buffer(0)));
        } else if (frame instanceof PongWebSocketFrame) {
            // 接收到PONG帧
            System.out.println("Received PONG frame");
        } else {
            // 其他类型的帧，继续传递给下一个处理器
            ctx.fireChannelRead(frame);
        }
    }
}