写一个java 接收 WebSocket 发送 Ping 控制帧

下面是一个简单的 Java 代码示例，用于接收 WebSocket 发送的 Ping 控制帧：

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.WebSocket;
import java.nio.ByteBuffer;
import java.util.concurrent.CompletionStage;

public class WebSocketClient {

    public static void main(String[] args) throws Exception {
        HttpClient client = HttpClient.newHttpClient();
        WebSocket webSocket = client.newWebSocketBuilder()
                .buildAsync(URI.create("wss://example.com/"), new WebSocketListener())
                .join();

        // Send a Ping control frame
        ByteBuffer buffer = ByteBuffer.wrap(new byte[]{0x9, 0x0});
        webSocket.sendPing(buffer);

        // Wait for the WebSocket connection to close
        webSocket.waitUntilClosed();
    }

    static class WebSocketListener implements WebSocket.Listener {

        @Override
        public void onPing(WebSocket webSocket, ByteBuffer message) {
            // Handle the Ping control frame
            System.out.println("Received Ping control frame: " + message);
        }

        @Override
        public CompletionStage<?> onClose(WebSocket webSocket, int statusCode, String reason) {
            System.out.println("WebSocket closed with statusCode: " + statusCode + ", reason: " + reason);
            return WebSocket.Listener.super.onClose(webSocket, statusCode, reason);
        }
    }
}

在这个示例中，我们使用 Java 11 中的 WebSocket API 来创建一个 WebSocket 连接，并在连接建立后发送一个 Ping 控制帧。当服务器响应 Ping 控制帧时，WebSocketListener 中的 onPing() 方法将被调用，并打印出接收到的消息。最后，我们等待 WebSocket 连接关闭。