为什么我的UDP client/server 数据报不在双向通信？

Question

我在两个应用程序之间设置了一个简单的 UDP client/server 数据报：Android-Java-Client 和 Windows-C#-Server。这是我的第一个 Java 编程和 Android 应用程序，因此解决方案可能很明显。所以我成功地从客户端向服务器发送了一个数据包。但是，我无法从服务器发送回客户端。

我正在尝试将确认消息从服务器发送回客户端。我尝试将 C# 客户端代码与现有的 C# 服务器代码合并，但一旦服务器收到第一条消息 System.ObjectDisposedException，它就会崩溃。我删除并重新开始 "See edited if you want"。现在，我已成功发送到服务器，但未收到任何内容，Java 客户端也未显示任何内容。我知道我可以（或者应该）使用相同的套接字发送回客户端。 我的错误在哪里？请和谢谢。

我试着把整个 NetworkThread 放在 OnTouchListener
我尝试将 SendUdpMessage() 分成两部分，一个用于发送，一个用于接收
我尝试了以下答案

而且我仍然无法让它工作:(

C# 服务器端：

// This class is responsible of running the server side on the PC. 
class UdpServer
{
    static void Main(string[] args)
    {
        byte[] data = new byte[1024];
        UdpClient serverSocket = new UdpClient(15000);
        int i = 0;

        while (true)
        {
            Console.WriteLine("Waiting for a UDP client...");
            IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
            data = serverSocket.Receive(ref sender);

            string stringData = Encoding.ASCII.GetString(data, 0, data.Length);
            Console.WriteLine("Response from " + sender.Address);
            Console.WriteLine("Message " + i++ + ": " + stringData + "\n");

            // Here I am sending back
            byte[] data2 = Encoding.ASCII.GetBytes("Response");
            serverSocket.Send(data2, 8, sender);
        }

    }
}

Java 客户端：一个按钮调用一个函数来发送 UDP 消息，并将响应分配给一个全局变量，然后我尝试通过 TextBox

在屏幕上显示

    public class MainActivity extends AppCompatActivity {

    String message;
    String Response;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Button Declaration
        final TextView TextOne = (TextView) findViewById(R.id.StatusText);
        Button LftBtn = (Button) findViewById(R.id.LeftButton);
        // ...
        // other code here (button declaration and event handlers
        // ...

        // Left Button Click
        LftBtn.setOnTouchListener(
                new Button.OnTouchListener() {
                    public boolean onTouch(View v, MotionEvent event) {
                        if (event.getAction() == MotionEvent.ACTION_DOWN) {
                            //Button pressed
                            TextOne.setText("Left");
                            message = "Left";
                            SendUdpMsg(message);
                            TextOne.setText(Response);
                            return true;
                        } else if (event.getAction() == MotionEvent.ACTION_UP) {
                            //Button released do nothing
                            return true;
                        }
                        return false;
                    }//onTouch
                });//setOnTouchListener
    }

    // This function is responsible for sending a udp packet to a hardCoded IP below. Returns nothing and takes a string(the message) as a parameter.
    public void SendUdpMsg(final String msg)
    {
        Thread networkThread = new Thread() {

            // No local Host 127.0.0.1 in Android
            String host = "192.168.200.3"; // my actual IP
            int port = 15000;
            DatagramSocket dsocket = null;
            String Response = "1";

            public void run() {
                try {
                    // Get the Internet address of the specified host
                    InetAddress address = InetAddress.getByName(host);

                    // wrap a packet
                    DatagramPacket packet = new DatagramPacket(
                            msg.getBytes(),
                            msg.length(),
                            address, port);

                    // Create a datagram socket, send the packet through it, close it.
                    dsocket = new DatagramSocket();
                    dsocket.send(packet);

                    // Here, I am receiving the response?
                    byte[] buffer = new byte[1024];
                    DatagramPacket packet2 = new DatagramPacket(buffer, buffer.length);
                    dsocket.receive(packet2);
                    Response = new String(buffer, 0, packet2.getLength());
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run()
                        {
                            // I can't use this since TextOne is a local variable in the above function
                            //TextOne.setText(Response);
                        }
                    });
                    dsocket.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }//catch
            }//run
        };// Networkthread
        networkThread.start();//networkThread.start() 
    }       
}

Answer 1

网络代码有效，问题是你没有等待响应，即 SendUdpMsg 方法不能 return 立即响应，它应该由后台线程推送。例如：

dsocket.receive(packet2);
Response = new String(buffer, 0, packet2.getLength());

// we received the response
// but since we are running on a background thread, we can not touch the UI
runOnUiThread(new Runnable() {
    @Override
    public void run() {
        // this is executed on the main (UI) thread
        TextOne.setText(Response);                        }
});

dsocket.close();

必须在后台线程上工作并在主线程上处理结果是一种常见模式。 Android 提供了一些工具，例如 Handler or AsyncTask

Answer 2

所以我将其添加到我的 SendUdpMsg() 中：

runOnUiThread(new Runnable() {
    @Override
    public void run()
           {
                 final TextView TextOne = (TextView) findViewById(R.id.StatusText);
                 TextOne.setText(Response);
           }
});`

终于成功了！单击按钮我成功发送 message 并收到 Response .

使命： 我想点击我的手机开始从笔记本电脑的网络摄像头流式传输实时视频，并将其显示到我的手机屏幕上。

请求：我这种双向沟通的方法好吗？如果没有最好的是什么？

为什么我的UDP client/server 数据报不在双向通信？

Why my UDP client/server datagram is not operating the two-way communication?

c#

java

sockets

android

udp