wifi断开后，Android socket仍然可以正常写入

Question

我编写了一个 Android 套接字演示，它只是将用户的输入发布到服务器。
我通过wifi连接从android客户端建立了一个socket，一切顺利，服务器可以接收到android客户端发送的消息。问题是，然后我关闭了手机的WIFI，但是socket可以正常写入。

安卓客户端代码:

public class MyActivity extends Activity {
    private SocketHandlerThread thread;

    /**
     * Called when the activity is first created.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        thread = new SocketHandlerThread("ScoketTest");
        thread.start();
    }

    class SocketHandlerThread extends HandlerThread {
        private Socket socket;
        private Handler handler;

        public SocketHandlerThread(String name) {
            super(name);
        }

        public SocketHandlerThread(String name, int priority) {
            super(name, priority);
        }

        @Override
        public void run() {
            try {
                socket = new Socket("192.168.60.184", 1990);
            } catch (IOException e) {
                Log.e("SocketTest", e.getLocalizedMessage(), e);
            }
            super.run();
        }

        Handler getHandler() {
            if (handler == null) {
                handler = new Handler(getLooper());
            }
            return handler;
        }

        void send(final String text) {
            Runnable runnable = new Runnable() {
                public void run() {
                    Log.e("SocketTest", "Start send text: " + text);
                    try {
                        socket.getOutputStream().write((text + "\n").getBytes());
                        socket.getOutputStream().flush();
                    } catch (Exception e) {
                        Log.e("SocketTest", e.getLocalizedMessage(), e);
                    }
                    Log.e("SocketTest", "Text has been send:" + text);
                }
            };
            getHandler().post(runnable);
        }

        @Override
        protected void onLooperPrepared() {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    findViewById(R.id.button).setEnabled(true);
                }
            });
        }
    }

    public void send(View view) {
        String text = ((EditText) findViewById(R.id.text)).getText().toString();
        thread.send(text);
    }
}

服务器代码:

public class SocketTestServer {
    ServerSocket serverSocket;

    SocketTestServer() throws IOException {
        serverSocket = new ServerSocket(1990);
    }

    void start() throws IOException {
        Socket clientSocket = serverSocket.accept();
        clientSocket.getInputStream();
        PrintWriter out = new PrintWriter(System.out, true);
        BufferedReader in =
                new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            out.println(inputLine);
        }
    }

    public static void main(String[] args) throws IOException {
        SocketTestServer server = new SocketTestServer();
        server.start();
    }
}

我尝试了几部手机。在 Galaxy Nexus(4.2.1) 上按预期抛出异常，但在某些 MOTO 或 HTC 手机上，套接字仍然可以毫无异常地写入，这意味着我可能会丢失一些我认为已成功接收的消息。
我怎么知道任何类型的手机上的套接字连接都断开了？

任何建议将不胜感激。

附言
我知道连接更改广播，但在接收广播之前，客户端可能已经通过损坏的套接字写入了一些消息。

虽然在应用协议(protocol)上添加接收检查可以解决消息丢失的问题，但我更喜欢保证 TCP 协议(protocol) promise 的传输层的可靠性。

Answer 1

我在我的套接字中使用 Writer & IOException，它工作正常。试试这个:

public static void sendUTF(String str)
    {
        try
        {
            outWriter.write(str + '\n');
            outWriter.flush();
        } 
        catch (IOException e)
        {
            e.printStackTrace();
            outServ.setText("Connection lost!");
        }
    }

public static Writer outWriter = new OutputStreamWriter(outputStream, "UTF-8");