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Unformatted text preview: nt and the server. Server software accepts
request for service from client software and returns the results of processing the
request to the client. The client then manipulates the received results and presents
it in the proper format to the user.
LAN or WAN or an Internet of Networks
Notice that the central feature of a client-server computing architecture is the
allocation of application-level tasks between clients and servers. The computers
and the operating systems of a client and a server may be different. For example, a
client may be a PC running MS-Windows OS, whereas a server may be a
mainframe system running Unix OS. In fact, there may be a number of different
types of client computers and operating systems and a number of different types of
server computers and operating systems in a single client-server computing
environment. As long as a particular client and server share the same
communications protocol and support the same applications, these lower-level
differences are irrelevant. It is the communications protocol that enables client and
server to inter-operate. One such standard communications protocol is the TCP/IP.
In a client-server computing environment, it is common for one server to use the
services of another server, and hence to be both a client and a server at the same
time. For example, suppose a client-server computing environment has clients, a
file server, and a disk block server. Any client can send a file access request to the
file server. On receiving such a request, the file server checks the access rights,
etc. of the user but does not actually read/write the file blocks itself. Instead, it
sends a request to the disk server for accessing the request data blocks. The disk
block server returns to the file server the requested data blocks. The file server
then extracts the actual data from the data blocks and returns it to the client. In this
scenario, the file server is both a server and a client. It is a server for the clients,
but a client for the disk block server. Hence the concept of client and server
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This document was uploaded on 04/07/2014.
- Spring '14