抓取WebSocket推送的消息

小灰灰 2022-05-14 06:21 358阅读 0赞

## 介绍 ##

很多直播或对数据及时性要求比较高的网站，使用了WebSocket。这种数据要怎么抓呢？

我们这里以socket.io为例，我们可以查看网站网页源代码看使用的H5的WebSocket还是socket.io等JS库。

这里以java语言为例说明。假定网站使用的是socket.io库来实现消息推送。我们如何通过java来获取服务端推送的信息呢？

socket.io提供了java的客户端实现socket.io-client。所以获取服务端推送的数据，本质是作为一个客户端连接上WebSocket server。

## 连接websocket server接收推送的数据 ##

### 首先添加依赖 ###

<dependency>
      <groupId>io.socket</groupId>
      <artifactId>socket.io-client</artifactId>
      <version>1.0.0</version>
    </dependency>

### ws地址的java代码 ###

final Socket socket = IO.socket("http://localhost:9098/");
    socket.on(Socket.EVENT_CONNECTING, new Emitter.Listener() {
            @Override
            public void call(Object... objects) {
                System.out.println("WebSocket连接中");
            }
        }).on(Socket.EVENT_CONNECT, new Emitter.Listener() {
            @Override
            public void call(Object... objects) {
                System.out.println("WebSocket连接成功！");
            }
        }).on("OnMSG", new Emitter.Listener() { // 这里指定要接收的事件名称
            @Override
            public void call(Object... objects) {
                JSONObject object = (JSONObject) objects[0];
                System.out.println("OnMSG:\n"+object.toString());
            }
        }).on(Socket.EVENT_DISCONNECT, new Emitter.Listener() {
            @Override
            public void call(Object... objects) {
                System.out.println("WebSocket连接关闭！");
            }
        });
    // 连接websocket server
    socket.connect();
    // 休眠3S后发送一条信息给websocket server
    Thread.sleep(3000L);
    if (socket.connected()) {
        JSONObject msg = new JSONObject();
        msg.put("from","jack");
        msg.put("to","admin");
        msg.put("content","Hello,I am jack!");
        socket.emit("OnMSG", msg);
    }

如果websocket地址是ws://localhost:9098，则在socket.io-java中地址写[http://localhost:9098][http_localhost_9098]；如果是wss://localhost:9098，则写为[https://localhost:9098][https_localhost_9098].

服务端的例子参考：[socketio推送技术][socketio]。

### wss地址的java代码 ###

public HostnameVerifier getMyHostnameVerifier() {
        return new HostnameVerifier() {
            @Override
            public boolean verify(String s, SSLSession sslSession) {
                return true;
            }
        };
    }
    public X509TrustManager getTrustManager() {
        return new X509TrustManager() {
            @Override
            public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                return new java.security.cert.X509Certificate[] {};
            }
            @Override
            public void checkClientTrusted(X509Certificate[] certs, String authType) {
            }
            @Override
            public void checkServerTrusted(X509Certificate[] certs, String authType) {
            }
        };
    }
    public SSLContext createSSLContext(X509TrustManager trustManager) throws GeneralSecurityException, IOException {
    // Security.insertProviderAt(new BouncyCastleProvider(), 1);
        try {
            TrustManager[] trustAllCerts = new TrustManager[]{trustManager};
            // Install the all-trusting trust manager
            SSLContext sc = SSLContext.getInstance("SSL");
            sc.init(null, trustAllCerts, new java.security.SecureRandom());
            return sc;
        } catch (Exception exception) {
            exception.printStackTrace();
        }
        return null;
    }
    X509TrustManager trustManager = getTrustManager();
    SSLContext sslContext = createSSLContext(trustManager);
    HostnameVerifier myHostnameVerifier = getMyHostnameVerifier();
    OkHttpClient okHttpClient = new OkHttpClient.Builder()
            .hostnameVerifier(myHostnameVerifier)
            .sslSocketFactory(sslContext.getSocketFactory(), trustManager)
            .build();
    // default settings for all sockets
    IO.setDefaultOkHttpWebSocketFactory(okHttpClient);
    IO.setDefaultOkHttpCallFactory(okHttpClient);
    // set as an option
    IO.Options opts = new IO.Options();
    opts.callFactory = okHttpClient;
    opts.webSocketFactory = okHttpClient;
    opts.port = 443;
    opts.secure = true;
    final Socket socket = IO.socket("http://localhost:9098/", opts);
    ...
    其他部分的代码参考ws部分

在浏览器中，在websocket请求的Frames部分是发送和接收到消息。如图：  
![2140342.jpg][]  
向上箭头（绿色）表示向websocket server发送的消息，向下箭头（红色）表示接收的消息。

## 注意 ##

有些网站可能对url上加了token或其他参数验证，防止不可靠的连接，一般比如会员登录后，生成token并发起websocket连接。这就需要自己处理token。

[http_localhost_9098]: http://localhost:9098
[https_localhost_9098]: https://localhost:9098
[socketio]: http://tommy88.top/2018/03/08/socketio%E6%8E%A8%E9%80%81%E6%8A%80%E6%9C%AF/
[2140342.jpg]: http://omh46px9n.bkt.clouddn.com/18-3-21/2140342.jpg