Question

我正在学习Socket编程，我想设计一个简单的程序，它能够在2个端口之间发送和接收消息。我使用相同的IP地址127.0.0.1，它应该是localhost，但设置2个不同的端口，代表两个不同的人互相发送消息。我打开2个终端来运行Class Demo2和Class Demo2B，以便在两个类之间发送和接收消息。但是，我看不到收到的任何消息。我可以知道我的代码出了什么问题吗？

这是Demo2

public class Demo2 {
public static void main(String[] args) throws SocketException {
    DatagramSocket sendSocket = new DatagramSocket();
    DatagramSocket receiveSocket = new DatagramSocket(7705);  //Set the Demo2 will use port 7705 to receive data
    new Thread(new send(sendSocket)).start();
    new Thread(new send(receiveSocket)).start();
}

static class send implements Runnable {
    private DatagramSocket datagramSocket;
    private send(DatagramSocket datagramSocket) {
        this.datagramSocket = datagramSocket;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        String line = null;
        try {
            while ((line=bufferedReader.readLine())!=null) {
                if(line.equals("88")) {
                    break;
                }
                byte[] buf = line.getBytes();
                DatagramPacket datagramPacket = new DatagramPacket(buf, buf.length, InetAddress.getByName("127.0.0.1"), 8805);  //set the data from Demo2 will be sent to port 8805
                datagramSocket.send(datagramPacket);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            throw new RuntimeException("Fail to send");
        }
    }

}

class receive implements Runnable {
    private DatagramSocket datagramSocket;
    private receive(DatagramSocket datagramSocket) {
        this.datagramSocket = datagramSocket;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        while(true) {
            byte[] buf = new byte[1024];
            DatagramPacket datagramPacket = new DatagramPacket(buf, buf.length);
            try {
                datagramSocket.receive(datagramPacket);
                String ip = datagramPacket.getAddress().getHostAddress();
                String data = new String(datagramPacket.getData(), 0, datagramPacket.getLength());
                System.out.println(ip+":"+data);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                throw new RuntimeException("Fail to send");
            }
        }
     }

  }
}

这是Demo2B

public class Demo2B {
  public static void main(String[] args) throws SocketException {
    DatagramSocket sendSocket = new DatagramSocket();
    DatagramSocket receiveSocket = new DatagramSocket(8805);  //Set the Demo2B will use port 8805 to receive data
    new Thread(new send(sendSocket)).start();
    new Thread(new send(receiveSocket)).start();
}

static class send implements Runnable {
    private DatagramSocket datagramSocket;
    private send(DatagramSocket datagramSocket) {
        this.datagramSocket = datagramSocket;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        String line = null;
        try {
            while ((line=bufferedReader.readLine())!=null) {
                if(line.equals("88")) {
                    break;
                }
                byte[] buf = line.getBytes();
                DatagramPacket datagramPacket = new DatagramPacket(buf, buf.length, InetAddress.getByName("127.0.0.1"), 7705);  //set the data from Demo2 will be sent to port 7705
                datagramSocket.send(datagramPacket);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            throw new RuntimeException("Fail to send");
        }
    }

}

class receive implements Runnable {
    private DatagramSocket datagramSocket;
    private receive(DatagramSocket datagramSocket) {
        this.datagramSocket = datagramSocket;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        while(true) {
            byte[] buf = new byte[1024];
            DatagramPacket datagramPacket = new DatagramPacket(buf, buf.length);
            try {
                datagramSocket.receive(datagramPacket);
                String ip = datagramPacket.getAddress().getHostAddress();
                String data = new String(datagramPacket.getData(), 0, datagramPacket.getLength());
                System.out.println(ip+":"+data);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                throw new RuntimeException("Fail to send");
             }
          }
       }

   }
 }

我希望看到的是，一旦我分别运行这两个类，如果我从Class Demo2发送消息到Class Demo2B，Demo2B应该能够捕获数据并显示它。与reverse相同，我可以从Class Demo2B回复到Class Demo2，Class Demo2也会捕获数据并显示它。如果有人能帮我解决这个困惑，我真的很感激。

Answer 1

在Demo2和Demo2B类中，您只初始化了发送线程。你忘了开始接收线程。

public class Demo2B {
  public static void main(String[] args) throws SocketException {
    DatagramSocket sendSocket = new DatagramSocket();
    DatagramSocket receiveSocket = new DatagramSocket(8805);  //Set the Demo2B will use port 8805 to receive data
    new Thread(new send(sendSocket)).start();
// This sould be new Thread(new receive(receiveSocket)).start();
    new Thread(new send(receiveSocket)).start();
}

因此，在以下两个类中更改以下代码：将解决问题：

new Thread(new send(sendSocket)).start();
new Thread(new receive(receiveSocket)).start();

因为你只能将这两个类之间的差异设为port，所以你可以简单地将一个类和供应端口作为一个参数来监听。

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1 个答案: