Java 为什么我的简单应用程序不接收UDP数据包

我试图创建一个简单的应用程序，将接收来自WiFi模块的UDP数据包。WiFi模块每5秒发送一个数据包，但我一直无法成功接收

使用Toast作为调试的一种方式，我以正确的顺序接收它们，直到“这里也没有收到”，这告诉我问题出在“socket.receive（packet）”行

有人知道为什么它可能不起作用吗？我还通过在线查看大量问题/示例来尝试代码的变体，但它们都会导致“socket.receive（packet）”行出现问题

另外，我编写了一个python脚本来做同样的事情，在同一个端口上查找UDP数据包，并使用QPython运行它，它确实接收数据包，因此数据包似乎是由WiFi模块发送的，平板电脑接收的，只是由于某种原因，应用程序无法读取数据

任何帮助或见解都将不胜感激，谢谢

代码如下：

public void run() {

    Toast.makeText(this, "RIGHT BEFORE TRY", Toast.LENGTH_LONG).show();

    DatagramSocket socket;
    DatagramPacket packet;


   try {
        Toast.makeText(this, "IN THE TRY", Toast.LENGTH _LONG).show();
        socket = new DatagramSocket(9750);
        byte[] buf = new byte[1024]; //buffer
        socket.setSoTimeout(100000);
        Toast.makeText(this, "Timeout is: " + socket.getSoTimeout(), Toast.LENGTH_LONG).show();
        //DatagramPacket packet = new DatagaramPacket(buf, buf.length);
        //Toast.makeText(this, "PACKET SIZE IS: "+buf.length, Toast.LENGTH_LONG).show();

        // while(true) {
        Toast.makeText(this, "IN THE WILD!", Toast.LENGTH_LONG).show();
        packet = new DatagramPacket(buf, buf.length);
        Toast.makeText(this, "PACKET SIZE IS: " + buf.length, Toast.LENGTH_LONG).show();

        try {
            //socket.receive(packet);
            socket.receive(packet);
            Toast.makeText(this, "GOT SOMETHING!", Toast.LENGTH_LONG).show();
        }
        catch (Exception i) {
            // TODO Auto-generated catch block
            //i.printStackTrace();
            Toast.makeText(this, "DIDN'T GET IT HERE EITHER!", Toast.LENGTH_LONG).show();
        }
        //byte[] result = new byte[packet.getLength()];
        byte[] result = packet.getData();
        System.arraycopy(packet.getData(), 0, result, 0, packet.getLength());
        String msg = new String(result);
        Toast.makeText(this, msg, Toast.LENGTH_LONG).show();
        Toast.makeText(this, "END WHILE!", Toast.LENGTH_LONG).show();
        //}

    } catch (Exception e) {
        // TODO Auto-generated catch block
        //e.printStackTrace();
        Toast.makeText(this, "DIDN'T GET IT!", Toast.LENGTH_LONG).show();

    }

}

---

更新：在前两个答案之后，看起来我们试图在主线程中执行网络操作，这是不可行的，因此我们目前正在尝试使用另一个线程或异步任务来实现它。希望有一些好消息：）

正如您所说，存在NetworkOnMainThread异常，您只需要将此问题放到新线程上并启动它

Thread thread = new Thread() {
    @Override
    public void run() {
Toast.makeText(this, "RIGHT BEFORE TRY", Toast.LENGTH_LONG).show();

    DatagramSocket socket;
    DatagramPacket packet;


   try {
        Toast.makeText(this, "IN THE TRY", Toast.LENGTH _LONG).show();
        socket = new DatagramSocket(9750);
        byte[] buf = new byte[1024]; //buffer
        socket.setSoTimeout(100000);
        Toast.makeText(this, "Timeout is: " + socket.getSoTimeout(), Toast.LENGTH_LONG).show();
        //DatagramPacket packet = new DatagaramPacket(buf, buf.length);
        //Toast.makeText(this, "PACKET SIZE IS: "+buf.length, Toast.LENGTH_LONG).show();

        // while(true) {
        Toast.makeText(this, "IN THE WILD!", Toast.LENGTH_LONG).show();
        packet = new DatagramPacket(buf, buf.length);
        Toast.makeText(this, "PACKET SIZE IS: " + buf.length, Toast.LENGTH_LONG).show();

        try {
            //socket.receive(packet);
            socket.receive(packet);
            Toast.makeText(this, "GOT SOMETHING!", Toast.LENGTH_LONG).show();
        }
        catch (Exception i) {
            // TODO Auto-generated catch block
            //i.printStackTrace();
            Toast.makeText(this, "DIDN'T GET IT HERE EITHER!", Toast.LENGTH_LONG).show();
        }
        //byte[] result = new byte[packet.getLength()];
        byte[] result = packet.getData();
        System.arraycopy(packet.getData(), 0, result, 0, packet.getLength());
        String msg = new String(result);
        Toast.makeText(this, msg, Toast.LENGTH_LONG).show();
        Toast.makeText(this, "END WHILE!", Toast.LENGTH_LONG).show();
        //}

    } catch (Exception e) {
        // TODO Auto-generated catch block
        //e.printStackTrace();
        Toast.makeText(this, "DIDN'T GET IT!", Toast.LENGTH_LONG).show();

    }


    }
};
thread.start();

---

您是否已将

添加到AndroidManifest.xml中？另外，您能在

catch

block中打印出

i.toString（）

吗？pelya，我有权限声明，我刚刚添加了i.toString（）。i.toString（）的结果是：2！android.os.NetworkOnMainThreadExceptionEkant Sharma最初在没有超时功能的情况下尝试了这个功能，因为我知道它默认为无限，但它仍然不起作用，所以我添加了这个功能来使用它。