Building web applications using Codeigniter (Installing Codeigniter)

Codeigniter is a powerful PHP framework which can be simply used to create full featured web applications.   This framework is based on the MVC Architecture. Here I am using Netbeans IDE as the editor. 

MVC Architecture

MVC or Model View Controller Architecture is a well known software designing pattern in creating web applications.One of the main advantage or a purpose of using MVC is to seperate business logic and the application data from the presentation layer. Model is the one who carries business logic and the application data. It handles data processing. Controller works as the mediator and converts input as commands for the model or the view. View is the interface shown to the user simply view is the presentation. Codeigniter is using this MVC architecture in it.

Get start with Codeigniter

Requirements

1.WAMP server

2. Netbeans IDE (as the editor)

Install codeigniter
1. Download Codeigniter. Latest version can be downloaded from Codigniter official website.
2. Unzip the package.
3. Upload the CodeIgniter folders and files to your server. (eg:- www folder of WAMP server. Create a folder with your project name and copy Codigniter files and folders into it).
4. Then, create a Netbeans project. Create a new PHP project with existing sources and select the folder you created.

 

5. Run the project. You will see the welcome message of Codeigniter in your browser.

6. Here are some important notices.

•  If you are using a database, edit application/config/database.php according to your database settings. 
•  Edit application/config/config.php to set your base URL. Location of your project folder. (eg:- if hosted in localhost,   http://localhost/ProjectName/)

taadaaa.... You have successfully installed codeigniter. Now you can create your own app...

MPI program to send two messages from multiple processors to one processor

MPI is a language independent communication protocol used in parallel programming. It a message passing library specification where data is directly sent to processes via messages. MPI is not an implementation. MPI is designed for high performance on both massively parallel machines and on workstation clusters. MPI provides a powerful, efficient, and portable way to express parallel programs. Message passing in MPI can be point to point operations or global operations.  MPI was explicitly designed to enable libraries. MPI specification has been defined for both Fortran and C++ languages.
The main objective of MPI programming is to enable computers to communicate and perform one task collaborating with each other. Communication will be managed by clusters. There are three main functionalities of MPI. Process Management Functionalities, Point to point communication and collective calls. (Broadcaste calls).

Blocking send and receive:-

In a MPI program, one address space is used in communication. Within the communication world there is one specific problem to be addressed. All the elements within a particular group should communicate within that context. In data transmission, two processes are involved. (MPI_SEND and MPI_RECV). Buffers are used by both of these processes within the transmission process. In one buffer communication world, when the buffer is refreshed, data will be lost. Sender has to keep the data in the buffer (blocking send) until you make sure that the receiver has received all data. Receiver also should wait (blocking receive) until the data received. Data loss will be reduced by this mechanism. 

Code:-

#include "mpi.h"#include <stdio.h>#include "stdlib.h"

int main(int argc,char *argv[]) {    int tasks, rank, dest, source, error, source_id;    char incomemsg[20]="Acknowledgment",   outgoingmsg[10]="Generated";    
    MPI_Status Status;   
    char errorString[BUFSIZ];     
    int errorsize;
    error = MPI_Init(&argc,&argv); 
//initializing MPI environment      
    MPI_Comm_size(MPI_COMM_WORLD, &tasks);  
//get the number of processes    
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);  
//get the  ID's of processes     
if (error != MPI_SUCCESS) {
    printf("MPI initialization failed!\n");
    exit(1);
  }

if (tasks < 2) {
    printf("You need to have at least 2 processors to run this program!\n");
    MPI_Finalize();   // Quit if there is only one processor     exit(0);
  }
if (rank != 0) {
  dest = 0;  /*process 0 is the receiver. other processes are sending messages to process 0 */
        error = MPI_Send(&outgoingmsg, 1, MPI_CHAR, dest, 1, MPI_COMM_WORLD);
//receives acknowledgment from process 0
        error = MPI_Recv(&incomemsg, 1, MPI_CHAR, dest, 1, MPI_COMM_WORLD, &Status);
        printf("Process %d received %s message from Process %d \n", rank,&incomemsg, Status.MPI_SOURCE, Status.MPI_TAG);
       //error handling if (error != MPI_SUCCESS) {
MPI_Error_string(error, errorString, &errorsize);
fprintf(stderr, "%d: %s\n", rank, errorString);
MPI_Abort(MPI_COMM_WORLD, error);
}
}
         else {
for(int j=1; j<tasks ; j++){
  //process 0 receives multiple messages from other processes source =j;
  error = MPI_Recv(&outgoingmsg, 1, MPI_CHAR, source, 1, MPI_COMM_WORLD, &Status);
printf("Process %d received %s message from Process %d \n", rank,&outgoingmsg, source, Status.MPI_TAG);
source_id = Status.MPI_SOURCE;
//process 0 sends acknowledgement
error = MPI_Send(&incomemsg, 1, MPI_CHAR, source_id, 1, MPI_COMM_WORLD);

if (error != MPI_SUCCESS) {
MPI_Error_string(error, errorString, &errorsize); (stderr, "%d: %s\n", rank, errorString); MPI_Abort(MPI_COMM_WORLD, error); }            } }     
MPI_Finalize();  //finalizing MPI environment}

DNSChanger Check up

Internet is one of the main sources for malwares which damage our computers. Since last few months 'DNSChanger' which is kind of a Trojan, has ruled the world of malwares. Thus, FBI, America has repeated the warning that as many as half a million computers still infected with the malware could lose their Internet connections on July 9 because the agency is shutting down an expensive workaround to the problem.
This DNSChanger virus affects the Windows and MAC systems and it was around the Internet since 2007. What it basically does is changing the DNS settings used by the system. DNS (Domain Name System) is an Internet service that converts user-friendly domain names (www.google.lk) into the numerical Internet protocol (IP) addresses (192.232.134.52) that computers use to talk to each other. First, DNSChanger changes the computer’s DNS server settings to replace the ISP’s good DNS servers with rogue DNS servers operated by the criminal. Second, it attempts to access devices on the victim’s small office/home office (SOHO) network that run a dynamic host configuration protocol (DHCP) server (eg. a router or home gateway). Further, this virus can spread itself into other machines if you are using a LAN by changing the settings of the router. Making it worse, this will block you from accessing anti virus softwares too.
The Bottnet network which was used to spread this DNSChanger was disabled in last November by FBI, USA through their special mission called 'Ghost Click'. Moreover, most of the anivirus software companies have updated their products against this malware. Even though several actions took placed, it was found that about half a million affected computers are still have access to internet as its users are not aware about this malicious software. Thus, FBI has announced that these computers will lose their Internet connection from July 9 onwards.

Fortunately, there are no infected computers reported from Sri Lanka yet. But still you can have a check up for your computer for this DNSChanger at http://dns-ok.us/. If you get DNS Resolution = GREEN in green, you are safe. Else, if you get  DNS Resolution = RED in red, it is better to have a complete system scan and remove DNSChanger via an updated antivirus software.

Source : http://www.fbi.gov/news/stories/2011/november/malware_110911 

Populating a Drop-Down list using PHP and MySQL

In web based applications you may need to develop a drop-down list using elements taken from a database table. This code will help you to easily populate a drop-down list from a field of a database table.

 function get_dropdown($user){

         connect_to_db();

                if (!mysql_select_db('cars'))

                {

                    echo "could not select ('db')";

                }

                            $add_query = "SELECT names

                           FROM cars 

                             WHERE owner = '$user'

                            ";

                    $res = mysql_query($add_query);

               <select name="car" class="dropdownmenus" value="Select me">

     <option selected> Select Car </option>

     <?

           while ($row = mysql_fetch_array($res)) {

         extract($row);

           echo "<option value='$row'>$row[names]</option>";

           }

     ?>

     </select>

     }

Creating a horde module

After successfully configuring horde a new application can be easily created.

1. Working horde packs can be downloaded via, ftp://ftp.horde.org/pub/horde-webmail/.

2. Next download the horde skeleton module using GIT repository.

     $ git clone --depth 1 git://github.com/horde/horde.git

   $ cd horde

   $ cp -R skeleton/ /your/install/path/to/horde/

3. Move the new module to /var/www/html/horde directory.( Full installation guide including moving the folder and renaming the module is available at http://wiki.horde.org/CreatingYourFirstModule?referrer=HowTo )

4. Then Open /var/www/html/horde/config/registry.php. Add the following entry to the file.
(module name = skeleton)

 $this->applications['skeleton'] = array(

             'fileroot' => dirname(__FILE__) . '/../skeleton',

             'webroot' => $this->applications['horde']['webroot'] . '/skeleton',

             'name' => _("Skeleton"),

             'icon' => $this->applications['horde']['webroot'] . '/skeleton/themes/graphics/me.png',

             'status' => 'active',

             'menu_parent' => 'horde'     );

Installing Horde in Fedora 10

As an open source project Horde will work better on Linux platform. This will guide you to install horde together will http server, MySql, PostFix SMTP server and Dovecot IMAP server.

Horde version - 3.3.8
PHP version - 5.2.9
Dovecot version - dovecot v1.1.20

1. Installing Apache  server
        $ yum install apache server

2. Installing MySql server
        $ yum install mysql-server

3. Install PostFix and Dovecot servers
        $ yum install postfix
        $ yum install dovecot

4. Configure PosFix SMTP server and Dovecot IMAP server
         http://workaround.org/ispmail/etch

5. Move /hordre folder to /var/www/html/ folder

6. Start servers.
        $ service httpd start
        $ service mysqld start
        $ service postfix start
        $ service dovecot start

6. Run the setup.php file
         $ php horde/scripts/setup.php

7. Check whether horde is working
         http://localhost/horde

8. Can use the users in the virtual_users table to login into horde. But have  to use the full domain names as,

    john---> john@example.com

Installing Horde in WAMP

Here is a simple way to install Horde in WAMP (Windows, Apache, MySQL, PHP) server.

1. Extract downloaded  tarball “horde-latest.tar” in WAMP “www” folder. (It can be downloaded from  http://www.horde.org/download/horde )

2. In order to create database tables go to /scripts/sql and open ‘create.mysql.sql’ by import mode in wamp server.

3. Test horde using this URL. http://your-server/horde/test.php