Client and Server Architecture

Client-server computing or networking is a distributed application architecture that partitions tasks or work loads between service providers (servers) and service requesters, called clients.

Definition:

Client/Server is a mutual form of distributed system and also a network procedure. A client is said to be a Package Supplicant which appeal a process to the server. And a Server is said to be a Service Provider which satisfies the request for a client

Client/Server Devices:

Client devices hold the request and the received information over the network. 
Example:

Mobile, Desktop Computers.

Server devices hold the stored file and databases. 

Example:

Website 

Server is a software program, this also runs on PC???s. Servers satisfy the request of the client and deliver the data to the client through a network. It has more memory spaces. 

Example: Web Server. 

Common types of server are Webserver, Proxy Server, FTP Server, and Online Game Server.

One Server response to a multiple Clients, Which satisfies the request. 

Client requests to a Server. Then it waits and receives replies from the server. It will be connected with small number of Client at a time.

Server wait for a request from a client.Then it response to the clients request. It can communicate with multiple clients at a time. The server may communicate with other Server to respond a Client.

The interaction between client and server is often described using sequence diagrams. Sequence diagrams are standardized in the UML

A generic client/server architecture has two types of nodes on the network: clients and servers. As a result, these generic architectures are sometimes referred to as "two-tier" architectures.

Some networks will consist of three different kinds of nodes: server,application servers which process data for the clients, and database serverswhich store data for the application servers. This is called a three-tier architecture.

The advantage of an n-tier architecture compared with a two-tier architecture (or a three-tier with a two-tier) is that it separates out the processing that occurs to better balance the load on the different servers; it is more scalable. The disadvantages of n-tier architectures are:

It puts more load on the network.
It is much more difficult to program and test software than in two-tier architecture because more devices have to communicate to complete a user's transaction.

It puts more load on the network.

It is much more difficult to program and test software than in two-tier architecture because more devices have to communicate to complete a user's transaction.

In Peer to Peer model, all systems are connected one another.A Client is act as a Server to one system and that Server as a Client to another system. 

It has more flexibility in growing the system to handle large number of Clients.