In this Article we will introduce the Microsoft .NET Framework and ASP.NET.
We will address the evolution of Microsoft’s Active Server Platform and discuss how .NET improves upon Microsoft current Active Server offerings, including Active Server Pages.
First, however, let’s examine how the Internet works .
Before, we dive into the evolution of ASP, we should review some basic Web client/server fundamentals. At the highest level, communication in a Web-based environment occursbetween two entities:
(1) a Web client (most commonly a Web browser such as Internet Explorer or Netscape Navigator), which is an application that requests files from a Webserver, and (2) a Web server, which is a software application, usually residing on a server,that handles client requests. It’s easy to deduce that a server is a computer that serves something. In a Web environment,a server “serves” HTTP responses. A server generally has more processing power than a personal computer (PC) in order to handle a large number of simultaneous client requests. A Web server is a server that is capable of handling Web, or HTTP, requests. In the Microsoft world, this Web server is one part of Internet Information Services (IIS). Web browsers and servers communicate using a protocol called Transmission Control Protocol/Internet Protocol (TCP/IP). A protocol is simply a set of rules and procedures that define how two entities communicate. TCP/IP is actually composed of two parts, TCP and IP.
TCP, often referred to as a transport protocol, wraps data in a digital envelope, called apacket, and ensures that the data is received in the same state in which it was sent. IP,a network protocol, is responsible for routing packets over a network, like the Internet.In addition to TCP/IP, Web clients and servers use a higher-level protocol, called HyperText Transfer Protocol (HTTP). To clarify, let us use the analogy of sending a letter through the mail. The letter is analogous to HTTP. When writing a letter, you’ll probably write it in a language that the receiver understands, right? So, if you were a Web browser or server you would write your letter in HTTP rather than English. The envelope, which containsa mail-to and return address, is analogous to TCP and your friendly mail carrier is analogousto IP. The mail carrier ensures that your letter is delivered to the correct street address, in the correct city, in the correct state. Likewise, IP ensures that your TCP packet is delivered to the correct IP address. HTTP is a request-response type protocol that specifies that a client will open a connection to a server and then send a request using a very specific format. The server will then respond and close the connection. HTTP has the ability to transfer Web pages, graphics, and any other type of media that is used by a Web application. Effectively HTTP is a set of messages that a Web browser and server send back and forth in order to exchange information. The simplest HTTP message is GET, to which a server replies by sending the requested document. In addition to GET requests, clients can also send POST requests. POST requests are used most commonly with HTML forms and other operations that require the client to transmit a block of data to the server. That is basically how the Internet works. Now let’s see how we have arrived at ASP.NET.