从Android手机向PC（Windows）发送udp消息不起作用

Question

I want to send a UDP message from my android phone 4.2(client) to PC(server) using WIFI connection. My phone and PC are connected via wireless router. But no message is received from phone to mobile. I have also tested this code for PC to PC connection successfully. I have added internet permission to manifest.xml. I would be greatefull, if you could help me. Thank you. I have added this permission.

 <uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> 

Client:

@Override
    protected void onCreate(Bundle savedInstanceState)
    {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);




        Button button1 = (Button) findViewById(R.id.button1);
        final TextView tv = (TextView) findViewById(R.id.textView1);
        final TextView tv2= (TextView) findViewById(R.id.textView2);







        button1.setOnClickListener(new OnClickListener()
        {

            @Override
            public void onClick(View v) 
            {

                boolean morgan= isOnline();
                String s = String.valueOf(morgan);
                tv.setText(s);


                try{

                    //InetAddress ipaddress = InetAddress.getByName("localhost");
                    InetAddress ipaddress = InetAddress.getByName("192.168.10.11");
                    int port = 6500;
                    //byte[] buffer = new byte[1024]; // empty byte array
                    String msg ="hello goooooooogle"; // send this message to the server
                    byte [] b_array = msg.getBytes();

                    //on SERVER side DatagramSocket able to receive packets on 8080 port
                    DatagramPacket packet = new DatagramPacket(b_array, b_array.length, ipaddress, port);// DatagramPacket(byte[], byte_length, InetAddress, port_number)
                    DatagramSocket socket = new DatagramSocket();
                    socket.send(packet);
                    socket.close();

                }
                catch(Exception e)
                {
                    System.out.println(e);
                }
                }




        });   
    }

    public boolean isOnline() {

        Runtime runtime = Runtime.getRuntime();
        try {

            Process ipProcess = runtime.exec("/system/bin/ping -c 1 192.168.10.11");
            //Process ipProcess = runtime.exec("/system/bin/ping -c 1 8.8.8.8");
            int     exitValue = ipProcess.waitFor();
            return (exitValue == 0);

        } 
        catch (IOException e)         
        { e.printStackTrace(); } 
          catch (InterruptedException e) { e.printStackTrace(); }

        return false;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings)
        {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

Server

public class server 
{
    public static void main(String args[])
    {

        try{
            System.out.println("aaa");
            byte[] inbuf = new byte[1000]; // default size
            DatagramPacket packet = new DatagramPacket(inbuf, inbuf.length);

            DatagramSocket socket = new DatagramSocket(6500);
            socket.receive(packet);

            int numBytesReceived = packet.getLength();
            System.out.println(numBytesReceived);
            String s = new String(inbuf);
            System.out.println(s);
            //System.out.println(inbuf[2]);

            socket.close();
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
    }
}

Answer 1

When dealing with network operations on Android it is recommended to use a separate thread to perform such operations. So try isolating your code in the onClick() method into an AsyncTask to run it in the background.

private class SendMessageTask extends AsyncTask<String, Void, Void> {
 protected Void doInBackground(String... ip) {
     // run network socket code here
     return null;
 }
}

Then onClick() will contain something like this:

new SendMessageTask().execute("IP_HERE");

Obviously you can modify it to fit your needs. However, if you need to send more data during the lifetime of your app, you may want to use your own background thread. Here's a more detailed explanation to why network operations can't / shouldn't be done in the UI thread - http://www.androiddesignpatterns.com/2012/06/app-force-close-honeycomb-ics.html