Sunday, December 11, 2011

what is proxy ?

Definition: proxy: In communications, a proxy is something that acts as a server, but when given requests from clients, acts itself as a client to the real servers. Analogy: Consider talking to somebody who speaks a foreign language through a translator. You talk to the translator, who receives your statements, then regenerates something else completely to the other end. The translator serves as your proxy. Key point: The communication terminates at the proxy. In other words, the proxy doesn't forward data so much as it tears it completely apart. For example, an HTTP proxy doesn't forward every request sent through it. Instead, it first examines if it already has the requested web page in its cache. If so, then it returns that page without sending another request to the destination server. Because proxies completely terminate the communication channel, they are considered a more secure firewall technology than packet filters, because they dramatically increase the isolation between the networks. Key point: You will occasionally be scanned for proxies. ISPs scan their users for proxies. Hackers scan the Internet looking for proxies they can anonymize their connections with. Certain servers (like IRC servers) scan clients for proxies in order to prevent anonymous connections. Several websites maintain lists of such proxies.


Sunday, December 4, 2011

3-tier application

Courtesy : http://searchsoftwarequality.techtarget.com


A 3-tier application is an application program that is organized into three major parts, each of which is distributed to a different place or places in a network. The three parts are:
  • The workstation or presentation interface
  • The business logic
  • The database and programming related to managing it
In a typical 3-tier application, the application user's workstation contains the programming that provides the graphical user interface (GUI) and application-specific entry forms or interactive windows.
(Some data that is local or unique for the workstation user is also kept on the local hard disk.)
Business logic is located on a local area network (LAN) server or other shared computer. The business logic acts as the server for client requests from workstations. In turn, it determines what data is needed (and where it is located) and acts as a client in relation to a third tier of programming that might be located on a mainframe computer.
The third tier includes the database and a program to manage read and write access to it. While the organization of an application can be more complicated than this, the 3-tier view is a convenient way to think about the parts in a large-scale program.
A 3-tier application uses the client/server computing model. With three tiers or parts, each part can be developed concurrently by different team of programmers coding in different languages from the other tier developers. Because the programming for a tier can be changed or relocated without affecting the other tiers, the 3-tier model makes it easier for an enterprise or software packager to continually evolve an application as new needs and opportunities arise. Existing applications or critical parts can be permanently or temporarily retained and encapsulated within the new tier of which it becomes a component.
Contributor(s): Cheryl Gilbert
This was last updated in July 2000

OOPS Concept

Courtesy : http://www.java-questions.com


Q1) What is polymorphism?
Ans) Polymorphism gives us the ultimate flexibility in extensibility. The abiltiy to define more than one function with the same name is called Polymorphism. In java,c++ there are two type of polymorphism: compile time polymorphism (overloading) and runtime polymorphism (overriding).

Friday, December 2, 2011

The Best Free Online Project Management Software

By William Fenton


You're a small business looking to get organized. The technology's out there, you know that. The problem is you can't afford dedicated project management software. Or so you think. Luckily for you, I've waded through the Web to find four of the best options for small businesses on a budget. Forget cheap. It's got to be free. You have the right to remain organized whether you run OS XWindows 7, Red Hat, or some combination of the three, so I've only looked at online solutions. There will be plenty of opportunities to upgrade. Some might be worth it for your business. However, I'm interested in the top deals that don't demand a credit card.

Top 10 Open Source Web-Based Project Management Software

By : VIVEK GITE


Project management software is not just for managing software based project. It can be used for variety of other tasks too. The web-based software must provide tools for planning, organizing and managing resources to achieve project goals and objectives. A web-based project management software can be accessed through an intranet or WAN / LAN using a web browser. You don't have to install any other software on the system. The software can be easy of use with access control features (multi-user). I use project management software for all of our projects (for e.g. building a new cluster farm) for issue / bug-tracking, calender, gantt charts, email notification and much more.

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