How execute an another program (tcpdump) in android application?

Question

I want to develop one android application, which i can capture network packets via tcpdump. I have rooted my android emulator device and i have installed tcpdump for android. I can run tcpdump from terminal emulator regurarly.

Now i want to develop one android app that it can execute the following command:

tcpdump > test

My java class is:

package com.example.test1;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;


public class MainActivity extends Activity 
{

    private Process p;
    private TextView error;
    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);     
    }

    public void tcpdump( View v )
    {
        try 
        {
            p = Runtime.getRuntime().exec( "su" );
            p = Runtime.getRuntime().exec( "tcpdump > test" );
        }
        catch ( Exception e ) 
        {
            error = (TextView) findViewById( R.id.error_message );  
            error.setText( "1" );
        }
    }

    public void stop ( View v )
    {
        p.destroy();
    }
}

and my android xml file is:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.test1.MainActivity" >

    <TextView
        android:id="@+id/error_message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView1"
        android:layout_marginLeft="27dp"
        android:layout_marginTop="124dp"
        android:layout_toRightOf="@+id/textView1"
        android:text="Sniff"
        android:onClick="tcpdump" />

    <Button
        android:id="@+id/stop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button1"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="88dp"
        android:text="Stop"
        android:onClick="stop" />

</RelativeLayout>

While application is running, i cant find test txt file, from command:

p = Runtime.getRuntime().exec( "tcpdump > test" )

Thanks.

Answer 1

First, copy your tcpdump file in a well-known folder. Lets say, you use /sdcard/myfolder

Then, do the following:

 Runtime.getRuntime().exec(new String[]{"su", "-c", "chmod 777 /sdcard/my_folder/tcpdump"});
 Runtime.getRuntime().exec(new String[]{"su", "-c", "/sdcard/my_folder/tcpdump > /sdcard/my_folder/test"});

Of course, you can also use getExternalstoragedirectory to choose a folder and copy the tcpdump file in that