在Android中的数据报套接字上发送和接收UDP数据包

Question

I have two classes,one sender class and the other is the receiver class.Both of the sending and receiving apps stops after few seconds and close down. My sender class is :

    public class MainActivity extends Activity {
InetAddress receiverAddress;
DatagramSocket datagramSocket;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    try {
        datagramSocket = new DatagramSocket(4444);
    } catch (SocketException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    byte[] buffer = "0123456789".getBytes();
    byte[] address="192.168.1.101".getBytes();

    try {
        receiverAddress = InetAddress.getByAddress(address);
    } catch (UnknownHostException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    DatagramPacket packet = new DatagramPacket(
            buffer, buffer.length, receiverAddress, 4444);

    try {
        datagramSocket.send(packet);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }




}

My receiving or listening class is:

public class MainActivity extends Activity {
DatagramSocket datagramSocket;
DatagramPacket packet;
TextView tv1;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    tv1=(TextView)findViewById(R.id.textView1);
     try {
        datagramSocket = new DatagramSocket(80);
    } catch (SocketException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    byte[] buffer = new byte[10];
     packet = new DatagramPacket(buffer, buffer.length);

    try {
        datagramSocket.receive(packet);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    byte[] buff = packet.getData();

tv1.setText(buff.toString());

}

Thanks in advance for the help.

Answer 1

In Android you're not allowed to execute Network operations on the UIThread (Main-Thread)

To Fix this: Copy your network-code to a new Thread and let it run.

Answer 2

The port numbers in the "new DatagramSocket(...)" calls look weird. The client should create an "unbound" socket - simply use "new DatagramSocket();". The sender should bind to the port that the client sends to, ie "new DatagramSocket(4444);".

Answer 3

Source and destination port number should be same. Give same numbers in "DatagramSocket(xxx)". xxx must be same in both programs.