Vibrant MCSE BOOT Camp Notes :
Back : Contents : MCSE :

Client/Server Relationship

As PCs evolved and users became more sophisticated and hungry for even more information, there developed a need for a new type of computer: the server. A server is a piece of hardware that receives, processes, and replies to a query. It usually is or resides on a central computer. A server has the capability to handle multiple connections concurrently and from many different sources or clients. Traditionally, server hardware is in the form of powerful minicomputers. More recently, however, high-end PCs are being used as servers in many functions.

A client is a computer or software application that helps a user form and send a query and then displays the results of the queried information for the user. Practically any computer can be a client; in fact, most servers have client software installed on them as well.

Like automated teller machines (ATMs), client/server applications are based on transactions. The client sends a request to the server, similar to a customer sending a request to an ATM. Just as the outcome of the ATM transaction depends on what type of information the customer gives the ATM when prompted, so does the outcome of a client request for information from a server depend on the information given to the server.

The client sends a request to the server with the following information:

• Address for the server (Where do I ask for this information?)
• The request (What information do you want?)
• The return address for the information (Where do I send the information?)

There must be a common protocol that both the client and the server speak to communicate with one another. On the Internet that protocol is TCP/IP. The server does most of the work in the relationship: It waits for requests, processes them, and then sends the client the information requested.

Through some client/server applications, like Telnet and the World Wide Web, remote users can actually run applications on the server machine and manipulate data. For instance, remember the salespeople who were tracking sales through individual computers? Well, now they can log onto a central computer using a Telnet application and enter their individual sales figures. The sales data now can be processed together at a central location. Or, using a secure protocol and a more advanced technology, such as a Web server gateway, a user can enter the information on his or her own machine, where it is compiled and sent to the server. The connection time, therefore, only lasts as long as the transmission.

back