在Android上使用Socket.IO始终返回XHR轮询错误

Question

我正在编写一个需要连接到node.js服务器上运行的Socket.IO实例的Android应用程序.

尝试连接到实例并使用iOS设备传输数据可以完美地工作,但是当我尝试使用Android设备时,它会失败.

我正在使用Native java客户端,这是我在android端使用的代码:

mManager = new Manager(new URI("https://example.com"));
mSocket = mManager.socket("/users");

// socket events listeners
    mSocket.on(Socket.EVENT_CONNECTING, new Emitter.Listener() {
        @Override
        public void call(Object... args) {
            Log.v(TAG, "Caught EVENT_CONNECTING");
            for (Object obj : args) {
                Log.v(TAG, "Errors :: " + obj);
            }
        }
    }).on(Socket.EVENT_CONNECT, new Emitter.Listener() {
        @Override
        public void call(Object... args) {
            Log.v(TAG, "connected to the backend");
            Log.v(TAG, String.format("JSON Obj to emit: %s", jsonObject.toString()));
            mSocket.emit("hello_packet", jsonObject);
        }
    }).on(Socket.EVENT_RECONNECTING, new Emitter.Listener() {
        @Override
        public void call(Object... args) {
            Log.v(TAG, "Caught EVENT_RECONNECTING");
            for (Object obj : args) {
                Log.v(TAG, "Errors :: " + obj);
            }
        }
    }).on(Socket.EVENT_DISCONNECT, new Emitter.Listener() {
        @Override
        public void call(Object... args) {
            Log.v(TAG, "Socket disconnected");
        }
    }).on(Socket.EVENT_ERROR, new Emitter.Listener() {
        @Override
        public void call(Object... args) {
            Log.v(TAG, "Caught EVENT_ERROR");
            for (Object obj : args) {
                Log.v(TAG, "Errors :: " + obj);
            }
        }
    }).on(Socket.EVENT_CONNECT_ERROR, new Emitter.Listener() {
        @Override
        public void call(Object... args) {
            Log.v(TAG, "Caught EVENT_CONNECT_ERROR");
            for (Object obj : args) {
                Log.v(TAG, "Errors :: " + obj);
            }
        }
    });

    Log.v(TAG, "Connecting socket");
    mSocket.connect();

每当我尝试连接时(基本上一行mSocket.connect();)日志打印以下行:

05-07 22:41:36.684 15552-15552/com.my.app V/Main Activity: Connecting socket
05-07 22:41:36.699 15552-15858/com.my.app V/Main Activity: Caught EVENT_CONNECTING
05-07 22:41:36.926 15552-15866/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:41:36.926 15552-15866/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:41:38.189 15552-15884/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:41:38.189 15552-15884/com.my.app V/Main Activity: Errors :: 1
05-07 22:41:38.207 15552-15887/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:41:38.208 15552-15887/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:41:39.518 15552-15911/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:41:39.518 15552-15911/com.my.app V/Main Activity: Errors :: 2
05-07 22:41:39.531 15552-15915/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:41:39.531 15552-15915/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:41:41.846 15552-15949/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:41:41.846 15552-15949/com.my.app V/Main Activity: Errors :: 3
05-07 22:41:41.857 15552-15953/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:41:41.857 15552-15953/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:41:46.863 15552-16025/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:41:46.864 15552-16025/com.my.app V/Main Activity: Errors :: 4
05-07 22:41:46.879 15552-16029/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:41:46.879 15552-16029/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:41:51.883 15552-16126/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:41:51.883 15552-16126/com.my.app V/Main Activity: Errors :: 5
05-07 22:41:51.895 15552-16130/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:41:51.895 15552-16130/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:41:56.900 15552-16236/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:41:56.900 15552-16236/com.my.app V/Main Activity: Errors :: 6
05-07 22:41:56.921 15552-16240/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:41:56.921 15552-16240/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:42:01.927 15552-16357/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:42:01.927 15552-16357/com.my.app V/Main Activity: Errors :: 7
05-07 22:42:01.945 15552-16361/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:42:01.945 15552-16361/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:42:06.951 15552-16466/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:42:06.952 15552-16466/com.my.app V/Main Activity: Errors :: 8
05-07 22:42:06.969 15552-16470/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:42:06.970 15552-16470/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:42:11.975 15552-16545/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:42:11.976 15552-16545/com.my.app V/Main Activity: Errors :: 9
05-07 22:42:11.994 15552-16549/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:42:11.994 15552-16549/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:42:17.000 15552-16629/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:42:17.000 15552-16629/com.my.app V/Main Activity: Errors :: 10
05-07 22:42:17.012 15552-16633/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:42:17.012 15552-16633/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:42:22.017 15552-16710/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:42:22.017 15552-16710/com.my.app V/Main Activity: Errors :: 11
05-07 22:42:22.033 15552-16714/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:42:22.033 15552-16714/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:42:27.039 15552-16788/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:42:27.039 15552-16788/com.my.app V/Main Activity: Errors :: 12
05-07 22:42:27.056 15552-16792/com.my.app V/Main Activity: Caught EVENT_CONNECT_ERROR
05-07 22:42:27.056 15552-16792/com.my.app V/Main Activity: Errors :: io.socket.engineio.client.EngineIOException: xhr poll error
05-07 22:42:32.061 15552-16957/com.my.app V/Main Activity: Caught EVENT_RECONNECTING
05-07 22:42:32.062 15552-16957/com.my.app V/Main Activity: Errors :: 13

因此,在尝试连接后,我立即得到xhr轮询错误,并且所有后续连接尝试都会遇到相同的结果.

我看到一些帖子说这样的问题可能是由SSL证书问题造成的,尽管我用Socket.IO库使用的SSL上下文的任何尝试都没有用.

如果任何人知道我可以尝试使其工作,那将是非常好的.

如果缺少任何信息或代码样例,请告诉我,我会添加它们.

Answer 1

经过进一步测试,我发现以下内容:

1. 如果在遇到不同事件(即EVENT_ERROR)时调试套接字,则捕获的异常将包含从您尝试访问的地址收到的响应代码.
2. 在我的情况下,当我尝试使用HTTP访问我的服务器时,我收到了301响应代码,因为我尝试访问的URL会自动将我重定向到HTTPS地址.
3. 当我尝试访问HTTPS地址时,我收到了401响应代码 - 这意味着我的套接字发出的请求已经到达服务器但未经授权 - 原因是目标服务器已启用基本身份验证而我没有提供套接字请求标头中需要的凭据.
4. 在提供了所需的头文件之后,我设法正确地连接到套接字服务器,但是当发出请求时它失败了,我的套接字又回到了重新连接尝试循环 - 原因是我发送给服务器的JSON我的Android手机不是预期的格式,服务器无法接收该请求.

我用来为我的套接字请求添加基本身份验证标头的代码:

// Adding authentication headers when encountering EVENT_TRANSPORT
mSocket.io().on(Manager.EVENT_TRANSPORT, new Emitter.Listener() {
    @Override
    public void call(Object... args) {
        Transport transport = (Transport) args[0];
        // Adding headers when EVENT_REQUEST_HEADERS is called
        transport.on(Transport.EVENT_REQUEST_HEADERS, new Emitter.Listener() {
            @Override
            public void call(Object... args) {
                Log.v(TAG, "Caught EVENT_REQUEST_HEADERS after EVENT_TRANSPORT, adding headers");
                Map<String, List<String>> mHeaders = (Map<String, List<String>>)args[0];
                mHeaders.put("Authorization", Arrays.asList("Basic bXl1c2VyOm15cGFzczEyMw=="));
            }
        });
    }
});

如果在尝试使用Socket.IO时遇到XHR轮询错误,请确保与套接字服务器的连接可用且连接正确.最后,在我的情况下,这一切都围绕着需要基本身份验证的服务器,而我在联系服务器时却没有提供它.

此外,因为我在尝试解决此问题时遇到了一些解决方案 - 尝试通过HTTPS访问您的服务器时,通常不需要特殊的主机名验证程序或特殊的证书管理器.尽量避免使用此类解决方案,因为它们会严重损害您应用的安全性.

Answer 2

如果您忘记在选项中设置传输，也会发生这种情况

IO.Options opts = new IO.Options();
opts.transports = new String[]{WebSocket.NAME}; //or Polling.NAME 

Answer 3

我可以验证与我的情况类似的问题。我正在测试与开发服务器的 websocket 连接。没有 SSL，只是普通的 http。这是我的情况：

1. 使用 android studio 模拟器测试了应用程序 websocket 与开发服务器的连接 - 连接成功，没有错误。
2. 测试没有。(1) 以上用真机代替模拟器。"xhr poll error"消息失败。

3. 然后，经过这么多时间没有成功，我添加AndroidManifest.xml了以下内容：

   <application ... android:usesCleartextTraffic="true" ...>

我的项目目前面向 API 28，因此默认"usesCleartextTraffic"值为 false。现在一切正常。