Android 和桌面之间的消息传递

Question

我正在尝试制作一个 Android 应用程序，它能够向计算机发送消息并从中接收消息。这是非常基本的。问题是，我已经通过多播实现了这一点，尽管不完全是。我的应用程序能够从计算机接收消息（它使用我制作的 java 应用程序来接收和发送消息）。但是，当我尝试从设备向计算机发送消息时，消息没有到达计算机。我的意思是，申请。

桌面应用程序和 Android 应用程序都使用相同的客户端 - 服务器类。这就是让我如此困惑的原因。因为，当我使用相同的类时，为什么它以一种方式工作而不是另一种方式？我只是不不。

桌面应用程序在 windows 上运行。

此外，当 Android 应用程序收到一条消息时，它会按以下方式接收消息："Message 1��..." 应该收到消息的时间："Message 1"。我不知道这是否相关。

代码如下：

服务器Class:

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class MulticastSocketServer implements Runnable{

    final static String INET_ADDR = "224.0.0.3";
    final static int PORT = 8888;
    static String msg;

    public MulticastSocketServer(String message) throws UnknownHostException, InterruptedException {
        msg = message;
        Thread thread = new Thread(this);
        thread.start();
    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        // Get the address that we are going to connect to.
        InetAddress addr = null;
        try {
            addr = InetAddress.getByName(INET_ADDR);
        } catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        // Open a new DatagramSocket, which will be used to send the data.
        try (DatagramSocket serverSocket = new DatagramSocket()) {

            msg += "\0";

            for (int i = 0; i < 10; i++) {
                // Create a packet that will contain the data
                // (in the form of bytes) and send it.
                DatagramPacket msgPacket = new DatagramPacket(msg.getBytes(),
                        msg.getBytes().length, addr, PORT);
                serverSocket.send(msgPacket);

                System.out.println("Server sent packet with msg: " + msg);
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            serverSocket.disconnect();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

客户Class:

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import java.net.UnknownHostException;
import java.util.Timer;
import java.util.TimerTask;

public class MulticastSocketClient implements Runnable {

    final static String INET_ADDR = "224.0.0.3";
    final static int PORT = 8888;
    Connection360 conn;

    public MulticastSocketClient (Connection360 connection) throws UnknownHostException {
        conn = connection;
        Thread thread = new Thread(this);
        thread.start();
    }

    @Override
    public void run() {
        try{
            // Get the address that we are going to connect to.
            InetAddress address = InetAddress.getByName(INET_ADDR);

            // Create a buffer of bytes, which will be used to store
            // the incoming bytes containing the information from the server.
            // Since the message is small here, 256 bytes should be enough.
            byte[] buf = new byte[256];

            // Create a new Multicast socket (that will allow other sockets/programs
            // to join it as well.
            try (final MulticastSocket clientSocket = new MulticastSocket(PORT)){
                //Joint the Multicast group.
                clientSocket.joinGroup(address);

                System.out.println("Connected");

                //while (true) {
                    // Receive the information and print it.
                    DatagramPacket msgPacket = new DatagramPacket(buf, buf.length);
                    Timer timer = new Timer("tmr");
                    timer.schedule(new TimerTask() {
                        @Override
                        public void run() {
                            clientSocket.disconnect();
                        }
                    },10000);
                    clientSocket.receive(msgPacket);

                    String msg = new String(buf, 0, buf.length);
                    System.out.println("Socket 1 received msg: " + msg.substring(0, msg.indexOf("\0")));
                    conn.MessageReceived(msg.substring(0, msg.indexOf("\0")));
                    clientSocket.disconnect();
                //}
            } catch (IOException ex) {
                ex.printStackTrace();
            }
            }catch (UnknownHostException ex){

            }
    }
}

这个类是我为桌面应用程序制作的。我为 Android 应用程序制作的类是相同的，但我必须将 System.out.println() 更改为 Log.v()。至于其他的，完全一样。

所以，如果您碰巧知道会发生什么，我将非常感谢您对这个主题的帮助。

谢谢！

Answer 1

当您读取传入数据包时，您不使用它的大小而是使用缓冲区的大小：

String msg = new String(buf, 0, buf.length);
// should be:
String msg = new String(buf, 0, msgPacket.getLength());
// or even better:
String msg = new String(msgPacket.getData());

如果传入数据包较短，则缓冲区的其余部分包含随机数据，这就是您得到的数据。 Java 字符串不是以 NUL 结尾的，因此 msg.indexOf("\0") 不起作用。

Android 和桌面之间的消息传递

Messaging between Android and Desktop

java

sockets

android

desktop-application

multicastsocket