Anurag Bandyopadhyay

CLIENT

A client is a computer program that, as part of its operation, relies on sending a request to another computer program (which may or may not be located on another computer). For example, web browsers are clients that connect to web servers and retrieve web pages for display. Email clients retrieve email from mail servers. Online chat uses a variety of clients, which vary depending on the chat protocol being used. Multiplayer video games or online video games may run as a client on each computer. The term "client" may also be applied to computers or devices that run the client software or users that use the client software.

A client is part of a client–server model, which is still used today. Clients and servers may be computer programs run on the same machine and connect via inter-process communication techniques. Combined with Internet sockets, programs may connect to a service operating on a possibly remote system through the Internet protocol suite. Servers wait for potential clients to initiate connections that they may accept.

The term was first applied to devices that were not capable of running their own stand-alone programs, but could interact with remote computers via a network. These dumb terminals were clients of the time-sharing mainframe computer.

A client is a piece of computer hardware or software that accesses a service made available by a server. The server is often (but not always) on another computer system, in which case the client accesses the service by way of a network.^[1] The term applies to programs or devices that are part of a client–server model.

SERVER

A server is a running instance of an application (Software) capable of accepting request from the client and give response accordingly. Servers can run on any computer or dedicated computer, which is also often referred to as "the server", In many cases, a computer can provide several services and have several servers running. The advantage of running servers on dedicated computer is security. For this reason most of the servers are daemon processes and designed by the designers in such a way that it can run on specific computer(s).

Servers operate within a client-server architecture. Servers are computer programs running to serve the requests of other programs, the clients. Thus, the server performs some tasks on behalf of clients. The clients typically connect to the server through the network but may run on the same computer. In the context of Internet Protocol (IP) networking, a server is a program that operates as a socket listener.^[1]

Servers often provide essential services across a network, either to private users inside a large organization or to public users via the Internet. Typical computing servers are database server, file server, mail server, print server, web server, gaming server, and application server.^[2]

Numerous systems use this client server networking model including Web sites and email services. An alternative model, peer-to-peer networking enables all computers to act as either a server or client as needed.

In the client/server programming model, a server is a program that awaits and fulfills requests from client programs in the same or other computers. A given application in a computer may function as a client with requests for services from other programs and also as a server of requests from other programs.

CLIENT SERVER RELATIONSHIP

Client/server is a program relationship in which one program (the client) requests a service or resource from another program (the server). Although the client/server model can be used by programs within a single computer, it is a more important concept for networking.  In this case, the client establishes a connection to the server over a local area network (LAN) or wide-area network (WAN), such as the Internet. Once the server has fulfilled the client's request, the connection is terminated. Your Web browser is a client program that has requested a service  from a server; in fact, the service and resource the server provided is the delivery of this Web page. Both client programs and server programs are often part of a larger program or application. Because multiple client programs share the services of the same server program, a special server called a daemon may be activated just to await client requests. In marketing, the client/server was once used to distinguish distributed computing by personal computers (PCs) from the monolithic, centralized computing model used by mainframes. This distinction has largely disappeared, however, as mainframes and their applications have also turned to the client/server model and become part of network computing.