Question

我正在努力掌握Android上的UDP，所以我正在编写一个小型测试程序，在同一台机器上设置2个套接字，发送数据包并接收它。我认为这是直截了当的，但是出了点问题。我的代码是：

DatagramSocket server;
DatagramSocket client;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    // Initialize a client socket and a server socket using UDP
    try {
     server = new DatagramSocket();
     client = new DatagramSocket();
} catch (SocketException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
}

 // Server will now send some data
  String data = "This is a test";
  DatagramPacket sendPacket = new DatagramPacket(data.getBytes(), data.length(),
       client.getInetAddress(), client.getLocalPort());
  try {
   server.send(sendPacket);
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

  // Client has to receive and read the data
  byte[] buf = new byte[1024];
  DatagramPacket receivePacket = new DatagramPacket(buf, buf.length);
  try {
   client.receive(receivePacket);
   byte[] receivedData = receivePacket.getData();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

  server.disconnect();
  client.disconnect();
}

当我调试我的代码时，它进入最后一次尝试，在“client.receive(receivePacket);”但它永远不会从该函数调用返回。该数据包似乎从未收到，但我很难找到原因。

我希望有人可以帮我解决这个问题。

编辑：使用线程的新代码。在实际发送数据包之前调用“接收”。试图使用AsyncTask。

public class udpexample extends Activity {

    DatagramSocket server;
    DatagramSocket client;

    String data = "This is a test";

    private static final String TAG = "UDPExampleActivity";

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Log.i(TAG, "Starting");

        // Initialize a client socket and a server socket using UDP
        try {
            server = new DatagramSocket();
            client = new DatagramSocket();
        } catch (SocketException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        new ReceivePacket().execute();
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

        // Server will now send some data
        DatagramPacket sendPacket = new DatagramPacket(data.getBytes(), data.length(),
                client.getInetAddress(), client.getLocalPort());
        try {
            Log.i(TAG, "About to send");
            server.send(sendPacket);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    private class ReceivePacket extends AsyncTask<Void, Void, Void> {
        // Thread used to receive a packet

        @Override
        protected Void doInBackground(Void... params) {
            // Client has to receive and read the data
            byte[] buf = new byte[1024];            
            DatagramPacket receivePacket = new DatagramPacket(buf, buf.length);
            try {
                Log.i(TAG, "About to receive");
                client.receive(receivePacket);
                byte[] receivedData = receivePacket.getData();

                // Verify that the packet is identical to the one being sent
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return null;
        }

        protected void onPostExecute(Void result) {
            server.disconnect();
            client.disconnect();
        }
    } 
}

仍有同样的问题，它停止并等待接收，没有任何反应。

非常感谢，

Jary

Answer 1

我认为你正在发送数据包而接收器还没有收听。

先尝试client.receive(..)，然后server.send(..)。那样client将监听传入的数据包。当然，你必须在两个不同的线程中运行它。

Android：简单的UDP程序问题

1 个答案: