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Affichage des articles du 2008

Home network, IP adress behind a router, how it works?

If you're using a router to access the Internet, then, maybe, you have noticed that your computer IP address is not the same seen from a computer or server outside your local network. Your router is hiding your local adress and permit the sharing of one single access to the Internet. How is it working? The router uses a technique named NAPT (Network Address Port Translator). NAP ... What? Typically, several computers are linked to one router in a Small or Home Office (SOHO). This router has only one IP address and is providing this single access to the SOHO computers. Let's say that, in fact, SOHO is Pr. John Doe's local network. Pr. John Doe has one nice black and silver brand new laptop featuring a huge hard drive disk and the latest processor. He owns as well, one slow and an old dusty computer he uses from time to time to browse the net. Let call the first computer, computer B like Brilliant and the second one, computer C like Crappy. A is the name of the router. Compu...

Sockets

For a software engineer, a socket is a network interface. Programs talking to each other are sharing the same thread. There are two communication modes : connected : Stream Sockets unconnected : Datagram Sockets In connected mode, the excellent quality of transmission is achieved using TCP . Web browsing with HTTP, for example, is actually using TCP. TCP is informationlossless! The information reach the final destination in the original order and no data is lost. The protocol used by Datagram Sockets is UDP. A packet retrieving information must be implemented.

A discussion about "delete this" in C++

To test your C++ programming experience and curiosity, a pop quiz question could be : what can you say about the C++ expression "delete this"? In C++, "this" keyword is used in object member functions and is a pointer to the curent object. As a beginner, the answer seemed to be obvious to me: how the language can allow an object to commit suicide? Impossible, I thought. However, it's possible to "delete this". Deleting the current object does not cause compilation errors. Although "delete this" is accepted by compilation, its usage can lead to logic errors. Indeed, if this suicide is absolutely necessary, the following rules must be observed: 1. The object must be created via dynamic allocation using new operator. 2. No member function of the object is invoked on "this" object after suicide. 3. No member object of "this" object is called after suicide. 4. Nothing will use "this" object after suicide. P...

Begginners : How to learn VHDL!

VHDL is one of the most Hardware Description Language used. This Description Language has many advantages over the others: VHDL has powerful synthesis functions allowing a strong and friendly design reuse methodology. This single advantage is so strong designers should not look aside. Good digital designs are generic a parameterizable. They are easy to maintain, reuse and help to produce complex system quicker. So, How to learn VHDL? 1. Learn Boolean algebra/ Boolean logic This will give you a better comprehension about the logic of a digital circuit and an overview on how computation is done on basic circuits. http://en.wikibooks.org/wiki/Digital_Circuits 2. Learn Finite state machine and Sequential Logic. http://en.wikipedia.org/wiki/Finite_state_machine Those two notions are absolute prerequisite to start coding in VHDL. This done, you can start a VHDL tutorial and then you're ready for the next chapters.