A Simple IP Blocker Plugin for WordPress

In my post here, I had shown how to create a basic “Hello World” plugin that greets the user with a simple “hello world” message in the admin dashboard. Now, let me show you how to create a wordpress plugin that actually does something more useful. In this post, I shall discuss a plugin that restricts the number of login attempts a user can make to login to the admin dashboard of your wordpress site. It makes sense to do this to secure your dashboard from being broken into because an unauthorized user can do just about anything to your site if he manages to access your admin dashboard. This includes defacing your site, deleting your content and God knows what else!

We will call our plugin “Simple IP Blocker”. It will restrict the number of failed login attempts to a fixed number, say three. On the fourth attempt, the user will see an error message “IP address blocked”. The user will be blocked for the remainder of the day on which he made the three unsuccessful login attempts. He will be able to try again on the following day.

Now, let’s get down to the nuts and bolts of the actual plugin. The steps are:

  1. Create a folder for the plugin
  2. Create a PHP file for the code called index.php in that folder.
  3. Create a header for the plugin.
  4. Initialize the required constants.
  5. Create a database table through the activation hook.
  6. Create a function that hooks into wp_login_failed action.
    It logs the failed attempts in the database table and blocks the IP address of the user.
  7. Create a function that displays the logged data from the table.
  8. Hook the function in 7 into the admin_menu action so that the logged data can be displayed.
  9. Create a function that hooks into the login action ‘wp_authenticate’
    that will give an error on trying to login in after ip is blocked.
  10. Activate your plugin and test it.

Let us discuss these steps in detail:

1. Navigate to the wp-content folder in your wordpress installation. Go to the plugins sub folder in it.
Create a folder called “simple-ip-blocker”.

2. Create a blank file titled index.php using your text editor and save it in the folder created in step 1

3. Now, let’s create the header in the index.php file.
Print the following code in after the opening php tag in the index.php file:

<?php 
/ * 
* Plugin Name: My Simple IP Blocker 
*/ 
?>

4. We will initialize the following constants:

<?php 
global $wpdb; 
define("LOGIN_FAILURES", 3); 
define("IPBLOCKER_TABLE", $wpdb-&gt;prefix.'ip_blocker');
?>

5. The above step will create a new line in the plugins section of your wordpress installation and define
the necessary constants.

We need to create a database table to log and count failed login attempts.
We will do this by using the “register_activation_hook” function.
We will create a PHP function named “simple_ip_blocker_create_table”.
In this function, we will write a “CREATE TABLE” MYSQL query. We will execute it by calling $wpdb->query
function on the global $wpdb variable by passing the query in it as a parameter.

We will then pass the “simple_ip_blocker_create_table” function name in the “register_activation_hook” function.

The code is as follows:

<?php 

function simple_ip_blocker_create_table() { 

     global $wpdb, $table_prefix; 
     //mysql query $create_tab_query = 
"CREATE TABLE IF NOT EXISTS `".IPBLOCKER_TABLE."`( 
`id` bigint(20) NOT NULL AUTO_INCREMENT, 
`ip_addr` varchar(20) NOT NULL, `attempts` int(4) NOT NULL, 
`try_date` date NOT NULL, `is_blocked` tinyint(1) NOT NULL, 
PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8"; 

$wpdb->query($create_tab_query); } 

register_activation_hook( __FILE__, 'simple_ip_blocker_create_table' ); ?>

 

Explanation of table structure:

id – PRIMARY KEY
ip_addr – IP address of user trying to log in.
attempts – number of failed logins per user.
try_date – date on which user s trying to log in.
is_blocked – flag too indicate whether the user is blocked or not.

6. Next, we will create a function that will hook into “wp_login_failed”. We will call
this function simple_ip_blocker_reset_bruteforce. This function will fire whenever the
user tries to login but fails. We will maintain a counter in the $_SESSION. Each failed
login will increment the counter. On reaching 3 attempts, the IP blocked flag, is_blocked
will be marked as 1 to indicate that the particular user is blocked for the remainder of
the day. However, the user can try again on the next day. Each attempt is logged in the
database table we created. For the first failed attempt, a new row will be created in the
table. For subsequent attempts, that row will be updated.For the third failed login,
the “is_blocked” field of that row will be updated to 1.

Check out the code below:

<?php 

function simple_ip_blocker_reset_bruteforce() { 

@session_start(); 
global $wpdb, $table_prefix; 
if(!isset($_SESSION["brute_count"])) { 
$_SESSION["brute_count"] = 1; 
$query = "INSERT INTO ".IPBLOCKER_TABLE."(ip_addr, attempts, try_date, is_blocked) VALUES(%s, %d, %s, %d)"; 
$try_date = gmdate("Y-m-d"); 

$wpdb-&gt;query( $wpdb-&gt;prepare( 
        $query, 
        $_SERVER["REMOTE_ADDR"], 
        $_SESSION["brute_count"], 
        $try_date,
        0
      ) );
      
     }
     else
     {
      $_SESSION["brute_count"] = $_SESSION["brute_count"] + 1;
     
      $try_date = gmdate("Y-m-d"); 
       
       //check limit
        
      $check_query = "SELECT attempts FROM ".IPBLOCKER_TABLE." WHERE ip_addr = %s AND try_date = %s";
        
      $attempt_count = $wpdb-&gt;get_var($wpdb-&gt;prepare($check_query, $_SERVER['REMOTE_ADDR'], $try_date ));
    
       if($attempt_count &gt;= LOGIN_FAILURES)
       {
         unset($_SESSION["brute_count"]);
         
         $update_query = "UPDATE ".IPBLOCKER_TABLE." SET is_blocked = 1 WHERE ip_addr = %s AND try_date = %s";
         
         $wpdb-&gt;query($wpdb-&gt;prepare($update_query, $_SERVER['REMOTE_ADDR'], $try_date ));
         
         wp_redirect(site_url('/wp-admin/'));
         
         exit;
         
       }
       else{
         
        $query = "UPDATE ".IPBLOCKER_TABLE." SET attempts = %d WHERE ip_addr = %s AND try_date = %s";
        
        $wpdb-&gt;query( $wpdb-&gt;prepare( 
          $query,  
          $_SESSION["brute_count"],
          $_SERVER['REMOTE_ADDR'],
          $try_date
         ) ); 
         
         
       }
     } 
  }  

  add_action("wp_login_failed", "simple_ip_blocker_reset_bruteforce");
?>

 

7. So far so good. Now we will create a function to display the data of
failed logins in the wordpress backend. We will call this function
“simple_ipblocker_menu_callback”. It will simply query the database table
that we created and list out the information in tabular form.

See the code below:

<?php 

function simple_ipblocker_menu_callback() { 

  global $wpdb; 
  $get_history = "SELECT * FROM ".IPBLOCKER_TABLE; //&quot; LIMIT $offset, 10; 
  
  $history = $wpdb->get_results($get_history, ARRAY_A); ?> 
  <h1>Simple IP Blocker active!</h1> 
  <table border="0" cellspacing="5" cellpadding="5" class="widefat" > 
  <tr>
    <td>S. No.</td>
    <td>IP Address</td>
    <td>Login Attempts</td> 
    <td>Try Date</td>
    <td>Blocked</td> 
  </tr> 
  <?php foreach($history as $row){ ?>
    <tr>
      <td><?php echo $row["id"]; ?></td>
      <td><?php echo $row["ip_addr"]; ?></td>
      <td><?php echo $row["attempts"]; ?></td>
      <td><?php echo $row["try_date"]; ?></td> 
      <td><?php echo ($row["is_blocked"] == 1)?"blocked":"unblocked"; ?></td>
    </tr>
  <?php } ?> 
  </table> 
<?php } ?>

 

8. In this step, we will simply write some code to call the function created above whenever the user
clicks the link for the plugin in the admin sidebar on the left. See below:

<?php 

function simple_ipblocker_menu_add() { 

     add_menu_page("Simple IP Blocker", "Simple IP Blocker", "administrator", "simple-ip-blocker", "simple_ipblocker_menu_callback" ); 

} 

add_action("admin_menu", "simple_ipblocker_menu_add"); 

?>

 

9. The last function to be created is the function that checks if the user’s IP is blocked. If so,
the user will not be able to login to the admin dashboard on that day. However, the user may try
logging in on the next day again.
We will call this function “simple_ip_blocker_check_ip”. In this function, we will check if the user’s
IP address is marked 1 in the is_blocked field. If so, the user will be prevented from logging in.
The function hooks into “wp_authenticate” and hence will fire before every login attempt.

The code is as follows:

<?php 
       function simple_ip_blocker_check_ip() { 
               global $wpdb; 
               $try_date = gmdate("Y-m-d"); 
               $check_IP = "SELECT is_blocked FROM ".IPBLOCKER_TABLE." WHERE ip_addr = %s AND try_date = %s"; 
               $blocked = $wpdb-&gt;get_var( $wpdb-&gt;prepare( 
          $check_IP,  
          $_SERVER['REMOTE_ADDR'],
          $try_date
         ) );
         
    if($blocked == 1)
    {
      wp_die("IP address blocked!");
    }
  }

  add_action("wp_authenticate", "simple_ip_blocker_check_ip");
?>

 

10. Lastly, now that the coding is complete, we need to activate the “Simple IP Blocker” plugin listed in the
wp-admin and test it according to the functionality in the steps above.

The full listing is as follows:

<?php  
/*
* Plugin Name: My Simple IP Blocker
*/  
global $wpdb;

define("LOGIN_FAILURES", 3);
define("IPBLOCKER_TABLE", $wpdb->prefix.'ip_blocker');

function simple_ip_blocker_create_table()
{
  global $wpdb, $table_prefix;
  
  $create_tab_query = "CREATE TABLE IF NOT EXISTS `".IPBLOCKER_TABLE."`(
    `id` bigint(20) NOT NULL AUTO_INCREMENT,
    `ip_addr` varchar(20) NOT NULL,
    `attempts` int(4) NOT NULL,
    `try_date` date NOT NULL,
    `is_blocked` tinyint(1) NOT NULL,
    PRIMARY KEY (`id`)
  ) ENGINE=MyISAM  DEFAULT CHARSET=utf8";
  
  $wpdb->query($create_tab_query);
}

register_activation_hook( __FILE__, 'simple_ip_blocker_create_table' );


function simple_ip_blocker_reset_bruteforce()
{ 
   @session_start(); 
   
   global $wpdb, $table_prefix;
   
   if(!isset($_SESSION["brute_count"]))
   {
    $_SESSION["brute_count"] = 1; 
    
    $query = "INSERT INTO ".IPBLOCKER_TABLE."(ip_addr, attempts, try_date, is_blocked) VALUES(%s, %d, %s, %d)";
    
    $try_date = gmdate("Y-m-d");
    
    $wpdb->query( $wpdb->prepare( 
      $query, 
      $_SERVER["REMOTE_ADDR"], 
      $_SESSION["brute_count"], 
      $try_date,
      0
    ) );
    
   }
   else
   {
    $_SESSION["brute_count"] = $_SESSION["brute_count"] + 1;
   
    $try_date = gmdate("Y-m-d"); 
     
     //check limit
      
    $check_query = "SELECT attempts FROM ".IPBLOCKER_TABLE." WHERE ip_addr = %s AND try_date = %s";
      
    $attempt_count = $wpdb->get_var($wpdb->prepare($check_query, $_SERVER['REMOTE_ADDR'], $try_date ));
  
     if($attempt_count >= LOGIN_FAILURES)
     {
       unset($_SESSION["brute_count"]);
       
       $update_query = "UPDATE ".IPBLOCKER_TABLE." SET is_blocked = 1 WHERE ip_addr = %s AND try_date = %s";
       
       $wpdb->query($wpdb->prepare($update_query, $_SERVER['REMOTE_ADDR'], $try_date ));
       
       wp_redirect(site_url('/wp-admin/'));
       
       exit;
       
     }
     else{
       
      $query = "UPDATE ".IPBLOCKER_TABLE." SET attempts = %d WHERE ip_addr = %s AND try_date = %s";
      
      $wpdb->query( $wpdb->prepare( 
        $query,  
        $_SESSION["brute_count"],
        $_SERVER['REMOTE_ADDR'],
        $try_date
       ) ); 
       
       
     }
   } 
}  

add_action("wp_login_failed", "simple_ip_blocker_reset_bruteforce");  //plugin admin panel


//pre-authentication

function simple_ip_blocker_check_ip()
{
  //die('done');
  global $wpdb;
  
  $try_date = gmdate("Y-m-d");
  
  $check_IP = "SELECT is_blocked FROM ".IPBLOCKER_TABLE." WHERE ip_addr = %s AND try_date = %s";
  
  $blocked = $wpdb->get_var( $wpdb->prepare( 
        $check_IP,  
        $_SERVER['REMOTE_ADDR'],
        $try_date
       ) );
       
  if($blocked == 1)
  {
    wp_die("IP address blocked!");
  }
}

add_action("wp_authenticate", "simple_ip_blocker_check_ip");

function simple_ipblocker_menu_callback()
{ 

  global $wpdb;
  
  /* $page = (isset($_GET['pg']))?$_GET['pg']:1;
  
  $offset = ($page - 1) * 10; */
  
  $get_history = "SELECT * FROM ".IPBLOCKER_TABLE; //" LIMIT $offset, 10";
  
  $history = $wpdb->get_results($get_history, ARRAY_A);
  
  ?>
  <h1>Simple IP Blocker active!</h1>
    <table border="0" cellspacing="5" cellpadding="5" class="widefat">
      <tr>
        <td>S. No.</td>
        <td>IP Address</td>
        <td>Login Attempts</td>
        <td>Try Date</td>
        <td>Blocked</td>
      </tr>
      <?php 
        foreach($history as $row)
        {
          ?>
          <tr>
            <td><?php echo $row["id"]; ?></td>
            <td><?php echo $row["ip_addr"]; ?></td>
            <td><?php echo $row["attempts"]; ?></td>
            <td><?php echo $row["try_date"]; ?></td>
            <td><?php echo ($row["is_blocked"] == 1)?"blocked":"unblocked"; ?></td>
          </tr>
          <?php 
        }
      ?>
    </table>
  <?php
  
  
  
}  

function simple_ipblocker_menu_add()
{
  add_menu_page("Simple IP Blocker", "Simple IP Blocker", "administrator", "simple-ip-blocker", "simple_ipblocker_menu_callback" );
}  

add_action("admin_menu", "simple_ipblocker_menu_add");
//plugin admin panel end

?>

 

Create a Basic WordPress Plugin From Scratch

In my post here, I had shown you how to create a plugin from existing code. In this post, I will show how to create a basic ‘Hello World’ wordpress plugin from scratch.

First of all, create a ‘hello-world’ folder in your plugins subfolder under the wp-content folder of your wordpress installation.
Then, create a blank file in the ‘hello-world’ folder and name it ‘index.php’.
After that, open your index.php file and put the following code in it:

<?php
/*
Plugin Name: Hello World Plugin
Plugin URI: http://myexamplesite.com/hello-world
Description: A simple WordPress Hello World plugin
Version: 1.0
Author: Author Name 
Author URI: http://myownsite.com
License: GPL2
*/
 ?>

 

This will create a descriptive header in the listing of plugins under the plugins section in wp-admin.

Now create a simple hello_world function in the example index.php page like so:

<?php 

function hello_world()
{
     echo "<h1>Hello World!</h1>"; 
}

?>

But this function needs to be called somewhere to get its output.

To get the output, we need to add the following code to our index.php file.

<?php

function hello_world_callback()
{
      add_menu_page("Hello World", "Hello World", "administrator", "hello-world", "hello_world");
}

add_action("admin_menu", "hello_world_callback");

?>

The add_action function hooks into ‘admin_menu’ to create a link to the plugin in the admin sidebar on the left of your dashboard. On clicking this link, the ‘hello_world’ function is called and the output is displayed on that page.

We will get the output in wp-admin under the “Hello World” tab once we activate the plugin.

So the complete code that needs to be there in the index.php is the following:

<?php
/*
Plugin Name: Hello World Plugin
Plugin URI: http://myexamplesite.com/hello-world
Description: A simple WordPress Hello World plugin
Version: 1.0
Author: Author Name 
Author URI: http://myownsite.com
License: GPL2
*/

function hello_world()
{
     echo "<h1>Hello World!</h1>"; 
} 

function hello_world_callback() { 
     add_menu_page("Hello World", "Hello World", "administrator", "hello-world", "hello_world"); 
} 

add_action("admin_menu", "hello_world_callback");

?>

 

The video above shows the installation and working of the plugin.

Click the following link for a more detailed tutorial.

GUI Tic-Tac-Toe in Java Revisited

In my post found here I discussed a tic-tac-toe game coded in Java which was a version using a Graphical User Interface. The code listing for the classes and interfaces can be found in the same post. In this post I will discuss a Graphical User Interface (GUI) version of the same application with some additional features. The GUI tic-tac-toe app is based on a console application version found here. I shall only provide the changes and additions to the code listings here. Note that I will use the NetBeans IDE.

We will primarily make changes to the AWTBoard class. After making these changes, the user will be asked whether he really wants to quit when a game is in progress. If he clicks Cancel, the game will continue. If he clicks OK, the game will be terminated. If the game is over or not yet begun, the user will be able to stop the game as usual. See the video below the code listing to understand how it works.

package com.tictactoe.components;

import java.awt.*;
import java.awt.event.*;
import javax.swing.JOptionPane;

/**
 *
 * @author Dell
 */
public class AWTBoard extends Board implements ActionListener{
    
    private Button[][] buttons = new Button[3][3];
    private Frame f;
    private Label l;
    
    private Move currMove;
    private Game myGame;
    
    public AWTBoard()
    {
        super();
        f = new Frame("Tic-Tac-Toe");
        f.setSize(300, 300);
        
        
        Panel topPanel = new Panel();
        
        topPanel.setLayout(new BorderLayout());
        
        Panel p = new Panel();
        
        GridLayout grd = new GridLayout(3,3);
        
        p.setLayout(grd);
        
        for(int i = 0; i &lt; 3; i++)
        {
            for(int j = 0; j &lt; 3; j++)
            {
                buttons[i][j] = new Button();
                
                buttons[i][j].addActionListener(this);
                
                p.add(buttons[i][j], i, j); //problem
                
            }
        }
        
        topPanel.add(p, BorderLayout.CENTER);
        
        l = new Label();
        
        topPanel.add(l, BorderLayout.SOUTH);
        
        f.add(topPanel);

        /****Begin changes****/
        f.addWindowListener(new WindowAdapter(){ 
            
            public void windowClosing(WindowEvent e){ 
                
                if(myGame.isGameOver() || Game.getMovesTillNow() == 0)
                {
                    f.dispose(); 
                    System.exit(0);
                }else{
                    int result = JOptionPane.showConfirmDialog((Component) null, "Game in progress. Are you sure you want to quit?",
        "Message", JOptionPane.OK_CANCEL_OPTION);
            
                    if(result == 0)
                    {
                        f.dispose(); 
                        System.exit(0);
                    }
            
                }
            } 
            
        });
        /****End changes****/        

        //f.pack();
        f.setBounds(200, 200, f.getWidth(), f.getHeight());
        
        f.setVisible(true);
    }
    
    public void setGame(Game game)
    {
        myGame = game;
    }
    
    public void display()
    {
        for(int i = 0; i &lt; 3; i++)
        {
            for(int j = 0; j &lt; 3; j++) 
            {  

                buttons[i][j].setLabel( ""+cells[i][j] );
               
            } 
             
        }  
    }
    
    public void markCell(Move move, char mark)
    {
        if(move.isIsValid())
        {
            int i = move.getRow(); 
            int j = move.getColumn(); 
            cells[i - 1][j - 1] = mark;
            
            buttons[i - 1][j - 1].setLabel(""+mark);
        }
        else
        {
            //System.out.println("INVALID MOVE!\n\n");
            l.setText("INVALID MOVE!");
        }
    }
    
    public Label getStatusLabel()
    {
        return l;
    }
    
    public void actionPerformed(ActionEvent e)
    {
        Button b = (Button)e.getSource();
        
        for(int i = 0 ; i &lt; 3; i++ )
        {
            for(int j = 0; j &lt; 3; j++)
            {
                if(b == buttons[i][j])
                {
                    currMove = new Move();
                    currMove.setRow(i + 1);
                    currMove.setColumn(j + 1);
                    currMove.setIsValid(true);
                }
            }
        }
        
        
        synchronized(this)
        {
            this.notify();
        }
        
    }
    
    public Move getCurrMove()
    {
        return currMove;
    }
}

 

An elementary security plugin protecting admin dashboard

In this post, I shall discuss an elementary plugin that can protect your wordpress admin dashboard from frequent incorrect login attempts. The plugin redirects the user to the home page after a predetermined number of incorrect logins, three for example. However, if the user enters the correct password after three wrong attempts, the user is logged in to the dashboard. The code hooks into the wp_login_failed action hook and uses a counter variable stored in the session to keep track of the number of login attempts. The plugin backend only tells the administrator that the plugin is active (See image above). The code listing is given below:

<?php 
/* 
* Plugin Name: My Simple Security 
*/ 

function simple_security_reset_bruteforce($username){ 

  @session_start(); 
  if(!isset($_SESSION["brute_count"])) { 
    $_SESSION["brute_count"] = 1; 
  } else { 
    $_SESSION["brute_count"] = $_SESSION["brute_count"] + 1; 
    if($_SESSION["brute_count"] > 3) { 
    
      unset($_SESSION["brute_count"]); 
      wp_redirect(site_url()); 
      exit; 
    } 
  } 
} 

add_action("wp_login_failed", "simple_security_reset_bruteforce"); //plugin admin panel 

function simple_security_menu_callback() { 

  echo "<h1>Simple Security active!</h1>"; 
  
} 

function simple_security_menu_add() { 

  add_menu_page("Simple Security", "Simple Security", "administrator", "simple-security", "simple_security_menu_callback" ); 
  
} 

add_action("admin_menu", "simple_security_menu_add"); //plugin admin panel end 

?>

 

A recording of the plugin is given below:

 

To turn this into a plugin and use it in your wordpress:

  1. Create an empty folder in your plugins folder.
  2. Give it an easily understandable name.
  3. Then, create a blank file in any text editor.
  4. Copy the code from the code listing here, including the “<?php” at the start.
  5. Paste the code copied above in your blank file.
  6. Save this file as index.php in your empty folder created above.
  7. Go to the wp-admin and activate the plugin.
  8. Logout from admin and try logging in to wp-admin repeatedly with the wrong password.

It should work as shown in the video above.

Deploying Tic-Tac-Toe Java GUI app

In this post, we deploy our tic-tac-toe Java GUI app so that it can be invoked either by double-clicking it or through the command line. Note: These steps below were performed on a Windows system.

  1. First, assemble all the Java source files in a folder of your choice.
  2. Open your Command Prompt.
  3. Navigate to your chosen folder in the Command Prompt using the cd command. e.g. cd Java\progs\TicTacToeGUIDemo
  4. Compile all the Java source files with javac compiler. e.g. javac -d . *.java.
    * means all Java files in the current folder.
  5. After successful compilation, the root package of your app will appear as a folder. In our case it’s ‘com’.
  6. Now, we need to create a manifest file to help us create a java archive file or JAR file.
    This file can be used to launch the app just by double-clicking on it.
    It can also be invoked using the java command from Command Prompt. e.g. java -jar TicTacToe.jar
  7. Open Notepad and create a blank new file called manifest.mf
  8. In this file, type:Main-Class: com.tictactoe.gameplay.AWTTicTacToe. This is the main class name, qualified by the full package name.
  9. After step 8, be sure to add a blank new line in the text file manifest.mf
  10. Save the manifest file and close it.
  11. Go back to your Command Prompt.
    Type the following: jar cvmf manifest.mf  –jar file name–  –root package folder name–
    e.g. jar cvmf manifest.mf TicTacToe.jar com
  12. You will get some verbose output from the jar command. To open your jar file, you can follow either of the steps in step 6 above.

View the video below to see it all in action.

Coding Tic-Tac-Toe with a Graphical User Interface

In my post found here I discussed a tic-tac-toe game coded in Java which was a console application.
The code listing for the classes and interfaces can be found in the same post. In this post I will discuss a Graphical User Interface (GUI) version of the same application. I shall only provide the changes and additions to the code listings here. Note that I will use the NetBeans IDE.

First I shall discuss the changes to the Board class. Since we shall use inheritance, we shall change the accessibility of the cells from private to protected. This is the only change required. See the listing below.

package com.tictactoe.components;  
/**
 *
 * @author pratyush
 */
public class Board { 
 
    protected static char[][] cells; //change to Board class for inheritance
    
    public Board()
    {
        cells = new char[3][3]; 
        cells[0] = new char[]{' ', ' ', ' '}; 
        cells[1] = new char[]{' ', ' ', ' '}; 
        cells[2] = new char[]{' ', ' ', ' '};
    }
    
    public void display()
    {
        for(int i = 0; i &lt; 3; i++)
        {
            for(int j = 0; j &lt; 3; j++){ 
        if(cells[i][j] == ' ') 
        { 
          System.out.print((i+1)+", "+(j+1)+"\t"); 
        } 
        else{
          System.out.print(cells[i][j]+"\t"); 
        } 
      } 
      
      System.out.print("\n\n"); 
    } 
  } 
  
  public Move checkAvailable(Move move){ 
  
    int i = move.getRow(); 
    int j = move.getColumn(); 
    boolean boundValid = ((i >= 1 && i<= 3) && ( j >= 1 && j <= 3));
    
        boolean charValid = false; 
        if(boundValid)
        {
            charValid = (cells[i - 1][j - 1] == ' ');
        } 
        boolean netValid = (boundValid && charValid); 
        move.setIsValid(netValid); 
        return move;
    }
    
    public void markCell(Move move, char mark)
    {
        if(move.isIsValid())
        {
            int i = move.getRow(); 
            int j = move.getColumn(); 
            cells[i - 1][j - 1] = mark;
        }
        else
        {
            System.out.println("INVALID MOVE!\n\n");
        }
    } 
}

 

AWTBoard

Among the additions, we shall make a new Board class called AWTBoard which shall inherit all the properties of the Board class. However it shall add the functionalities of GUI from the Java Abstract Windowing Toolkit or AWT packages. The listing of this new class is given below. The AWT version of the Board will be a frame with a 3 X 3 grid of buttons with a status label at the bottom to display all the messages which were being outputted to the console in the console version of the application. The players will play their turns by clicking buttons in the grid.

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package com.tictactoe.components;

import java.awt.*;
import java.awt.event.*;

/**
 *
 * @author Dell
 */
public class AWTBoard extends Board implements ActionListener{
    
    private Button[][] buttons = new Button[3][3];
    private Frame f;
    private Label l;
    
    private Move currMove;
    
    public AWTBoard()
    {
        super();
        f = new Frame("Tic-Tac-Toe");
        f.setSize(300, 300);
        
        
        Panel topPanel = new Panel();
        
        topPanel.setLayout(new BorderLayout());
        
        Panel p = new Panel();
        
        GridLayout grd = new GridLayout(3,3);
        
        p.setLayout(grd);
        
        for(int i = 0; i &lt; 3; i++)
        {
            for(int j = 0; j &lt; 3; j++)
            {
                buttons[i][j] = new Button();
                
                buttons[i][j].addActionListener(this);
                
                p.add(buttons[i][j], i, j);
                
            }
        }
        
        topPanel.add(p, BorderLayout.CENTER);
        
        l = new Label();
        
        topPanel.add(l, BorderLayout.SOUTH);
        
        f.add(topPanel);
        
        f.addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){ f.dispose(); System.exit(0);} });
        
        
        f.setBounds(200, 200, f.getWidth(), f.getHeight());
        
        f.setVisible(true);
    }
    
    public void display()
    {
        for(int i = 0; i &lt; 3; i++)
        {
            for(int j = 0; j &lt; 3; j++) 
            {  

                buttons[i][j].setLabel( ""+cells[i][j] );
               
            } 
             
        }  
    }
    
    public void markCell(Move move, char mark)
    {
        if(move.isIsValid())
        {
            int i = move.getRow(); 
            int j = move.getColumn(); 
            cells[i - 1][j - 1] = mark;
            
            buttons[i - 1][j - 1].setLabel(""+mark);
        }
        else
        {
            
            l.setText("INVALID MOVE!");
        }
    }
    
    public Label getStatusLabel()
    {
        return l;
    }
    
    public void actionPerformed(ActionEvent e)
    {
        Button b = (Button)e.getSource();
        
        for(int i = 0 ; i &lt; 3; i++ )
        {
            for(int j = 0; j &lt; 3; j++)
            {
                if(b == buttons[i][j])
                {
                    currMove = new Move();
                    currMove.setRow(i + 1);
                    currMove.setColumn(j + 1);
                    currMove.setIsValid(true);
                }
            }
        }
        
        
        synchronized(this)
        {
            this.notify();
        }
        
    }
    
    public Move getCurrMove()
    {
        return currMove;
    }
}

 

First, let us see the constructor of the new Board class AWTBoard. We create a Frame which is basically a window. We then create a Panel and add it to the content pane of the window created previously. We create a Border Layout for the previously added Panel with a top part and a bottom part. To the bottom part, we add a label to display any status messages needed to be displayed. To the top part of the Panel, we create a Panel with a Grid Layout to add a 3 X 3 Grid of Buttons and then add this panel to the main Panel. The Players play the game by taking turns to click the buttons in this grid.

We override the display method of the Board class to mark the buttons of the grid instead of outputting them to the console. Likewise, we override all those other methods which output to the console. The new method added is the actionPerformed method which is basically an event handler that tells Java what to do when the buttons in the 3 x 3 grid are clicked. getStatusLabel and getCurrMove are helper methods to enable passing data in and out of GUI Board.

AWTTicTacToe

Apart from the GUI Board, we need to introduce another class called AWTTicTacToe which will contain changes to invoke the GUI Board instead of the console.

package com.tictactoe.gameplay;

import com.tictactoe.components.*;

/**
 *
 * @author pratyush
 */
public class AWTTicTacToe {  /**
    * @param args the command line arguments
    */
    public static void main(String[] args) {
        // TODO code application logic here 
        Game game = new Game(); 
        Player player1 = new Player(); 
        player1.setPlayerNum(1); 
        player1.setPlayerMark('X'); 
        player1.setGame(game); 
        Player player2 = new Player(); 
        player2.setPlayerNum(2); 
        player2.setPlayerMark('0'); 
        player2.setGame(game);
        
        //
        AWTBoard board = new AWTBoard();
        board.display();
        
        /*******/ 
        game.setWhoseTurn(player1); 
        game.setGameOver(false); 
        boolean status = game.isGameOver(); 
        // 
        do
        {
            int movesNow = Game.getMovesTillNow(); 
            if(movesNow == 9)
            {
                if(game.getWinner() == null)
                {
                    //
                    board.getStatusLabel().setText("TIE!\n");
                    break;
                }
            } 
            int turn = game.getWhoseTurn(); 
            //
            
            board.getStatusLabel().setText("PLAYER "+turn+" click a button\n"); 
            
            //
            try{
                synchronized(board)
                {
                    board.wait();
                }
            }
            catch(InterruptedException ie)
            {
                ie.printStackTrace();
            }
            
            Move move = board.getCurrMove();
            
            switch(turn)
            {
                case 1:
                    player1.makeMove(board, move); 
                    if(game.checkWinningMoves(player1))
                    {
                        game.setWinner(player1); 
                        //
                        board.getStatusLabel().setText("PLAYER 1 WINS!");
                        game.setGameOver(true);
                    }
                    else
                    {
                        if(move.isIsValid())
                        {
                            movesNow = Game.getMovesTillNow(); 
                            //
                            
                            board.getStatusLabel().setText("MOVE NUMBER "+movesNow+"\n");
                            game.setWhoseTurn(player2);
                        }
                    }
                break;
                case 2:
                    player2.makeMove(board, move); 
                    if(game.checkWinningMoves(player2))
                    {
                        game.setWinner(player2); 
                        //
                        
                        board.getStatusLabel().setText("PLAYER 2 WINS!");
                        game.setGameOver(true);
                    }
                    else
                    {
                        if(move.isIsValid())
                        {
                            movesNow = Game.getMovesTillNow(); 
                            // 
                            board.getStatusLabel().setText("MOVE NUMBER "+movesNow+"\n");
                            game.setWhoseTurn(player1);
                        }
                    }
                break;
                default:
                    //
                    board.getStatusLabel().setText("ERROR!\n");
                break;
            } 
            status = game.isGameOver();
        }
        while(!status); 
    } 
}

 

AWTTicTacToe is the main class containing the main method. It invokes the AWTBoard class instead of the Board class. It will not contain any statements to output to the console, although it may do so for debugging. To see the results of the invocation of this main class see the video below.

 

This GUI implementation of tic-tac-toe in Java is not perfect by any means. There is scope for improvement and new features can be added. Meanwhile, you can run this code and enjoy!

Convert Very Large Decimal Integers to Base 62 And Back

The other day I was trying to devise a way of converting arbitrarily large base 10 integers to the order of a billion billion to base 62 and did not get much help from the web. So I devised my own solution using the BC Math extension which ships with PHP by default. So, this solution works upto PHP_INT_MAX which is 9223372036854775807 for 64-bit platform. It also works upto 99 trillion on 32-bit-platform. I used an array as a stack to store successive remainders of division by the base, which is 62, and at the end popped them one by one from the stack to generate the converted base 62 number. The converse, multiplication by successive powers of 62 and addition of those powers helped to convert base 62 back to base 10.

First I used PHP OOPS to create a class called MyBase62Converter. The code is given below:

class MyBase62Converter
{
	private $base62StrVar = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
	private $baseInt = 62;
	
	function encode($decNum)
	{
		$base = $this->baseInt;
		
		$myStack = array();

		$remainder = 0;

		$base62Str = $this->base62StrVar;

		do 
		{
			
			$remainder = bcmod($decNum, $base);
			
			array_push($myStack, $remainder);
			
			$decNum = bcdiv(bcsub($decNum, $remainder), $base); 
			
		}
		while($decNum > 0);
		
		$binNum = '';

		while(count($myStack) > 0)
		{
			
			$binNum.= substr($base62Str, array_pop($myStack), 1);
		}

		return (strlen($binNum) >= 6)?$binNum: str_pad($binNum, 6, 0, STR_PAD_LEFT);
	}
	
	function decode($baseNum)
	{
		
		$base62Str = $this->base62StrVar;
		
		$base = $this->baseInt;

		$hashLen = strlen($baseNum);
		
		$decNum = '';
		
		for($i = 0; $i < $hashLen; $i++)
		{
			$decNum = bcadd($decNum, bcmul(bcpow($base, $i), strpos($base62Str , substr($baseNum, $hashLen - $i - 1, 1))));
		}
		
		return $decNum;
	}
	
}

Using the two simple encode and decode functions we can convert base 10 integers to base 62 representation and vice versa.

You can see the example below:

require_once("lib/class.MyBase62Converter.php"); 

$encoder = new MyBase62Converter();

echo "<br />";

echo PHP_INT_MAX." encoded is ".$encoded = $encoder->encode(PHP_INT_MAX);

echo "<br />";

echo $encoded." decoded is ".$decoded = $encoder->decode($encoded);

echo "<br />";
 
$largeNum = bcpow(62, 6) - 1; 

echo $largeNum." encoded is ".$encoded = $encoder->encode($largeNum); 

echo "<br />"; 

echo $encoded." decoded is ".$decoded = $encoder->decode($encoded); 

echo "<br />"; 

$veryLargeNum = bcpow(62, 7) - 1; //getting 0 due to num expressed in scientfic exponential notation 2.183401055849E+14 

echo $veryLargeNum." encoded is ".$encoded = $encoder->encode($veryLargeNum); 

echo "<br />"; 

echo $encoded." decoded is ".$decoded = $encoder->decode($encoded); 

echo "<br  />"; 

$max_num = 99999999999999; 

echo $max_num." encoded is ".$encoded = $encoder->encode($max_num , 62); //99999999999999 

echo "<br />"; 

echo $encoded." decoded is ".$decoded = $encoder->decode($encoded); 

echo "<br />"; 

$new_num = 63; 

echo $new_num." encoded is ".$encoded = $encoder->encode($new_num , 62);  

echo "<br />"; 

echo $encoded." decoded is ".$decoded = $encoder->decode($encoded);

The result of code execution is given below:

Simple File Searcher App: An Exercise in Concurrency

Here is a simple app for searching files on a computer. The app uses a recursive algorithm to compare names of files and folders with the search keyword and returns all the matches.

The procedure is as follows:

1.	list the roots of the filesystem
2.	for each root listed in step1:
	a.	list folders and files
	b.	for each file in a., compare keyword with file name.  
                If matched, list this file in results 
	c.	for each folder in a, 
		i.  compare keyword with folder name.  If matched, list this folder in results 
		ii. repeat 2a. for each folder
	d.	repeat a. to c. until no subfolders are found

The Java version is given below:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package com.filesearch.components;

import java.io.*;
import java.io.File.*;
import java.util.concurrent.*;
import java.util.Scanner;
/**
 *
 * @author Dell
 */
public class FileSearcherComponent implements Runnable{
    
    static String fileKeyword;
  
    static long count = 0;
  
    static File logFile;
  
    static BufferedWriter bw;
  
    private void logToFile(String path)
    {
  try{
    
    bw.write(path, 0, path.length());
    bw.newLine();
    
  }
  catch(IOException i)
  {
    i.printStackTrace();
  }
    }
    
    @Override
    public void run()
    {
  try{
      
    bw = new BufferedWriter(new FileWriter(logFile, true));
      
  }
  catch(IOException i)
  {
    i.printStackTrace();
  }
    
  long currTime = System.currentTimeMillis();
    
        File[] roots = File.listRoots(); //get drives
        
        for(File root:roots)
        {
            
            File rootFile = new File(root.getPath());
            
            traverseRoots(rootFile);
        }
    
  long endTime = System.currentTimeMillis();
    
  double seconds = (endTime - currTime) / 1000;
    
  System.out.printf("\n %d results in %f seconds.\n", count, seconds);
    
  try{
    
    bw.flush();
    
    bw.close();
  }
  catch(IOException i)
  {
    i.printStackTrace();
  }
    }
    
    private void traverseRoots(File root)
    {
        if(root.isDirectory())
        {
            
            String name = root.getName();

            if(name.contains(fileKeyword))
            {
                System.out.println(root.getAbsolutePath());
        
    logToFile(root.getAbsolutePath());
        
    count++;
            }
            
            File[] rootFolders = root.listFiles();

            if(rootFolders != null &amp;&amp; rootFolders.length &gt; 0){

                for(File rootFolder: rootFolders)
                {
                    if(rootFolder.isDirectory())
                    {
                        
                        String name1 = rootFolder.getName();

                        if(name1.contains(fileKeyword))
                        {
                            System.out.println(rootFolder.getAbsolutePath());
              
          logToFile(rootFolder.getAbsolutePath());
              
          count++;
                        }
                        
                        traverseRoots(rootFolder);
                    }
                    else if(rootFolder.isFile())
                    {
                        String name2 = rootFolder.getName();

                        if(name2.contains(fileKeyword))
                        {
                            System.out.println(rootFolder.getAbsolutePath());
              
          logToFile(rootFolder.getAbsolutePath());
              
          count++;
                        }
                    }
                    
                }
            }
        }
        else if(root.isFile())
        {
            String name3 = root.getName();

            if(name3.contains(fileKeyword))
            {
                System.out.println(root.getAbsolutePath());
        
    logToFile(root.getAbsolutePath());
        
    count++;
        
            }
        }
       
    }
    
    public static void main(String[] args)
    {
        FileSearcherComponent f = new FileSearcherComponent();
        
        ExecutorService es = Executors.newSingleThreadExecutor();
    
  logFile = new File("LOG.txt");
    
  if(logFile.exists())
  {
    logFile.delete();
  }
    
  try{
    
    logFile.createNewFile();
  }
  catch(IOException i)
  {
    i.printStackTrace();
  }
    
        System.out.print("Enter search keyword: ");
        
        fileKeyword  = new Scanner(System.in).nextLine();
    
        es.execute(f);	
    
    
    }
    
}

 

Copy, compile, run and ENJOY!

PHP Web Services: What they are, what they do and how to make one.

A “Web Service” is a bunch of code that resides on a server in an intranet or the internet. It performs some function and returns some data required by the client application that calls it. e.g. A foreign exchange web service might return the rates at which euros are converted to US dollars. A weather web service will return local temperature during any day. These web services can then be used in client applications like an e-commerce site that shows product prices in euros or dollars depending on the country the buyer is in, etc.

One common use of web services is in smartphone apps as a backend. A smartphone does not typically query a site’s database directly since it is not good to store database credentials locally on it. So the app calls a web service residing on a server. This web service fetches data from a web application and returns the data found to the smartphone app. e.g. An mobile e-commerce store allows users to search products by keywords. This app will call a web service which acts like a function that will accept the search keyword as a parameter. The web service returns a list of products to the calling app either as JSON or XML. The calling app will parse the results and display a list of products with names and images to the buyer.

But how is this achieved from the coding standpoint ? How does one create a PHP web service? There are many ways but I shall discuss about SOAP-based web services and illustrate with an example containing both the web service and the calling code in PHP. I will be using the NUSOAP library in my example. This will be an parameterized hello world web service. The client will call the web service and pass a name as a parameter to it. The result will be a
“Hello” greeting to the name given.

We need to do two things, (1) Setup the server side and (2) Setup the client side, from which we will call our web service.

DISCLAIMER: It is assumed that the reader knows basics of PHP development and can work on web servers or locally setup development servers.

Setting Up The Server Side

  1. Check SOAP is enabled on the server: Your server phpinfo() should look like this.If your phpinfo() does not look like the screenshot above, you need to locate your php.ini file and uncomment the semi-colon in the lines containing the soap DLL file (php_soap.dll in Windows). Save the modified php.ini and restart Apache Server. Then check your phpinfo() again.
  2. Create a new project folder on server.
  3. Install the PHP NUSOAP library: Download it from here.
  4. Extract the archive and keep the lib folder in your project folder.
  5. Call lib/nusoap.php in your PHP file where you will be working.
    <?php require('lib/nusoap.php'); //make sure that the nusoap.php file is found at this path relative to your php source file ?>
  6. Create a SOAP server object.
    <?php $soapServer = new soap_server(); //create the soap server object ?>
  7. Configure WSDL
    <?php $soapServer-&gt;configureWSDL("HelloWorldWSDL", "http://www.helloworldsite.com"); //configure the WSDL ?>
  8. Register a method with your SOAP server.
    <?php $soapServer-&gt;register('helloWorldWebSvc', array('name'=&gt;'xsd:string'),array('return'=&gt;"xsd:string"), "http://www.helloworldsite.com", "http://www.helloworldsite.com#helloWorldWebSvc", 'rpc', 'encoded', 'Hello World App!'); //register the method with the server ?>
  9. Make sure you call the service method of the SOAP server.
    <?php /*$soapServer-&gt;service($HTTP_RAW_POST_DATA); //Fault:SOAP-ENV:Client error in msg parsing: xml was empty, didn't parse! */ @$soapServer-&gt;service(file_get_contents("php://input")); //FIXED ?>
  10. Putting It All Together
    <?php 
    
    require("lib/nusoap.php"); 
    
    $soapServer = new soap_server(); //create the soap server object 
    
    $soapServer->configureWSDL("HelloWorldWSDL", "http://www.helloworldsite.com"); //configure the WSDL 
    
    $soapServer->register('helloWorldWebSvc', array('name'=&amp;gt;'xsd:string'),array('return'=&amp;gt;"xsd:string"), "http://www.helloworldsite.com", "http://www.helloworldsite.com#helloWorldWebSvc", 'rpc', 'encoded', 'Hello World App!'); //register the method with the server 
    
    function helloWorldWebSvc($name) //our function with business logic. Also called the server-side method. 
    { return "Hello $name!"; } 
    
    $HTTP_RAW_POST_DATA = isset($HTTP_RAW_POST_DATA)?$HTTP_RAW_POST_DATA:''; 
    /*$soapServer->service($HTTP_RAW_POST_DATA); //Fault:SOAP-ENV:Client error in msg parsing: xml was empty, didn't parse! */
    
    @$soapServer->service(file_get_contents("php://input")); //FIXED 
    
    exit; ?>

     

Important Note

It is important to note that there are outdated code snippets out there using $soapServer->service($HTTP_RAW_POST_DATA);

This wont work with NUSOAP in PHP 7. It will give the error:

Fault:SOAP-ENV:Client error in msg parsing: xml was empty, didn’t parse!

Fix it by using the following:

@$soapServer->service(file_get_contents(“php://input”));

Setting Up the Client Side

  1. Check SOAP is enabled on the server: This step is identical to its counterpart in the server-side above.
  2. Create a new project folder on server: This step is identical to its counterpart in the server-side above.
  3. Install the PHP NUSOAP library: This step is identical to its counterpart in the server-side above.
  4. Call lib/nusoap.php in your PHP file where you will be working: This step is identical to its counterpart in the server-side above.
  5. Create a SOAP client object.
    <?php $client = new nusoap_client("http://localhost/HelloSvc/hello_world_web_svc.php?wsdl"); ?>
  6. Call the server-side method.
    <?php $response = $client-&gt;call("helloWorldWebSvc", array("Some User")); //calling the registered method of the web service from client. ?>
  7. Putting It All Together
    <?php 
    
    require("lib/nusoap.php"); 
    
    $client = new nusoap_client("http://localhost/HelloSvc/hello_world_web_svc.php?wsdl"); 
    
    $response = $client->call("helloWorldWebSvc", array("Some User")); //calling the registered method of the web service from client 
    
    if($client->fault) { 
      
      echo "Fault:".$client->faultcode." ".$client->faultstring; 
      
    } else { 
    
      print_r($response); 
    
    } 
      
    exit; 
      
    ?>

 

 

Note: In Android and iOS apps, no PHP client is used generally. Instead coding is done in Java or Objective-C, etc that uses the HTTP Client API of the respective programming languages.

 

The End Result

If all goes well you will see a screen like the one below when you invoke the PHP Web Service client in your browser.

Note: This example is compliant with PHP 7.