Communicate Android Application to PC Application over Wifi

Question

I am making an Android Application which will send an UDP Broadcast over Wifi. And there is a PC program to receive it. Here is the code:

This is the user permission in the AndroidManifest.xml

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

DeviceManagerWindow.java

import android.net.wifi.WifiManager;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.view.Menu;

public class DeviceManagerWindow extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_device_manager_window);
        WifiManager wifi = (WifiManager)getSystemService( Context.WIFI_SERVICE );
        if(wifi != null)
        {
            WifiManager.MulticastLock lock = wifi.createMulticastLock("WifiDevices");
            lock.acquire();
        }
        Thread sendMulticast = new Thread(new MultiCastThread());
        sendMulticast.start();
    }

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

}

This file sends multicast packets:

MultiCastThread.java

public class MultiCastThread implements Runnable
{
    MulticastSocket s;
    DatagramPacket pack;
    public MultiCastThread()
    {
        try
        {
            s = new MulticastSocket(WifiConstants.PORT_NO);
            s.joinGroup(InetAddress.getByName(WifiConstants.GROUP_ADDR));
        }
        catch(Exception e)
        {
            Log.v("Socket Error: ",e.getMessage());
        }
    }
    @Override
    public void run()
    {
        try
        {
            pack = new DatagramPacket(WifiConstants.WHO_IS.getBytes(),WifiConstants.WHO_IS.getBytes().length, InetAddress.getByName(WifiConstants.GROUP_ADDR), WifiConstants.PORT_NO);
            s.setTimeToLive(WifiConstants.TIME_TO_LIVE);
            s.send(pack);
        }
        catch(Exception e)
        {
            Log.v("Packet Sending Error: ",e.getMessage());
        }
    }
}

WifiConstants.java

This file keeps records of the constants for Wifi Interaction.

public class WifiConstants
{
    public static final int PORT_NO = 5432;
    public static final String GROUP_ADDR = "225.4.5.6";
    public static final int DGRAM_LEN = 1024;
    public static final String WHO_IS = "Who is?";
    public static final int TIME_TO_LIVE = 100;
}

On my system I am running a java code to receive the packets and print it in the console.

ListenerDevice.java

package Receiver;

import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;


public class ListenerDevice
{
    public static final int PORT_NO = 5432;
    public static final String GROUP_ADDR = "225.4.5.6";
    public static final int DGRAM_LEN = 1024;
    public static final String WHO_IS = "Who is?";
    public static final int TIME_TO_LIVE = 1;
    public static void main(String[] args)
    {
        MulticastSocket socket = null;
        DatagramPacket inPacket = null;
        byte[] inBuf = new byte[DGRAM_LEN];
        try
        {
          //Prepare to join multicast group
          socket = new MulticastSocket(PORT_NO);
          InetAddress address = InetAddress.getByName(GROUP_ADDR);
          socket.joinGroup(address);

              while(true)
              {
                    System.out.println("Listening");
                    inPacket = new DatagramPacket(inBuf, inBuf.length);
                    socket.receive(inPacket);
                    String msg = new String(inBuf, 0, inPacket.getLength());
                    System.out.println("From :" + inPacket.getAddress() + " Msg : " + msg);
              }
        }
        catch(Exception ioe)
        {
            System.out.println(ioe);
        }
      }
}

This is sending data, but not receiving on the PC end. both the devices are connected to the same network.

I also created a class for receiving the packets on the mobile. and it is receiving the packets being sent.

What should I do for connecting this.

Answer 1

Both the devices should be connected to the same network . As you are sending packet from the Emulator to the PC, it resides on the same system. Therefore, you are not facing any problem with it. But as you will send the data packets from PC to the mobile device both the devices should share the same network.

It would be more efficient if both the devices connected to unfirewalled network. because firewall could create trouble in sending the data packets.

This is the conclusion I came upto.