UDP Client on Android

Question

I have made an UDP Server on a Wi-Fi demo board and test it using and android App (UDP Sender). I created my own UDP client apps on Android, but it doesn't work.

I created and configured well the socket port and the IPaddress but the app doesn't work and I don't know why.

PS : In the manifest I added the uses-permission to access to the Wi-Fi

her is my simple code

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class Udp_Client extends Activity {


    /** Called when the activity is first created. */
    TextView txt5,txt1;
    byte[] send_data = new byte[1024];
    Button hello;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        txt1   = (TextView)findViewById(R.id.textView1); 
        txt5   = (TextView)findViewById(R.id.textView5); 

        hello = (Button) findViewById(R.id.button1);






        hello.setOnClickListener(new View.OnClickListener(){             
            public void onClick(View v) {                 


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

            }  

         }); 


    }


    public void client() throws IOException{

            String str="Hello";
            int port = 50000;
         DatagramSocket client_socket = new DatagramSocket(port);
         InetAddress IPAddress =  InetAddress.getByName("192.168.0.1"); 

                        send_data = str.getBytes();


            DatagramPacket send_packet = new DatagramPacket(send_data,str.length(), IPAddress, port);
            //client_socket.setBroadcast(true);
            client_socket.send(send_packet);                      


            client_socket.close();

        }       

}

[1]: https://i.sstatic.net/aXPhf.png

Answer 1

I found the solution for the problem

The problem was in the manifest

Here is my new code and my manifest

The main in wich I call the UDP_Client :

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;


public class MainActivity extends ActionBarActivity implements View.OnClickListener {
    private TextView sceen = null;
    private Button launch = null;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        sceen = (TextView)findViewById(R.id.textView1);
        launch = (Button)findViewById(R.id.udpbutton);
        launch.setOnClickListener(this); 

       launch.setOnClickListener((OnClickListener) this); 

    }
           public void onClick(View v) {
               //UDP Client erstellen
               UDP_Client Client = new UDP_Client();
               Client.Message = "Your message";
                    Client.NachrichtSenden();






           }


    }

The code of my UDP_Client

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

import android.annotation.SuppressLint;
import android.os.AsyncTask;
import android.os.Build;

public class UDP_Client 
{

    private InetAddress IPAddress = null;
    private String message = "Hello Android!" ;
    private AsyncTask<Void, Void, Void> async_cient;
    public String Message;


    @SuppressLint("NewApi")
    public void NachrichtSenden()
    {
        async_cient = new AsyncTask<Void, Void, Void>() 
        {
            @Override
            protected Void doInBackground(Void... params)
            {   
                DatagramSocket ds = null;

                try 
                {
                    byte[] ipAddr = new byte[]{ (byte) 192, (byte) 168,43, (byte) 157};
                    InetAddress addr = InetAddress.getByAddress(ipAddr);
                    ds = new DatagramSocket(5000);
                    DatagramPacket dp;                          
                    dp = new DatagramPacket(Message.getBytes(), Message.getBytes().length, addr, 50000);
                    ds.setBroadcast(true);
                    ds.send(dp);
                } 
                catch (Exception e) 
                {
                    e.printStackTrace();
                }
                finally 
                {
                    if (ds != null) 
                    {   
                        ds.close();
                    }
                }
                return null;
            }

            protected void onPostExecute(Void result) 
            {
               super.onPostExecute(result);
            }
        };

        if (Build.VERSION.SDK_INT >= 11) async_cient.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
        else async_cient.execute();
    }
}

The manifest :

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.udp_server"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="21" />
    <uses-permission android:name="android.permission.INTERNET" />
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

I added the part of code in my manifest

hope that it will help someone in the future ;)

Answer 2

I think you miss this:

public void connect (InetAddress address, int port)

Of the DataGramSocket Object.

Try:

client_socket.connect(IPAddress, port);
client_socket.send(send_packet);