Introduction to Client Server Networks

Servers and clients are the building blocks of computer networks

Man drawing client server diagram on clear board

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Client-server networking grew in popularity years ago as personal computers became the alternative to older mainframe computers. Client-server networking refers to a computer networking model that uses both client hardware devices and servers, each with specific functions. The client-server model can be used on the internet as well as local area networks (LANs). Examples of client-server systems on the internet include web browsers and web servers, FTP clients and servers, and the DNS.

Client and Server Hardware

Client devices are typically PCs with network software applications installed that request and receive information over the network. In addition, mobile devices function as clients.

Servers store files and databases, including complex applications and websites. Servers typically feature higher-powered central processors, more memory, and larger disk drives than client devices.

Client-Server Applications

The client-server model organizes network traffic using a client application and client devices. Network clients send messages to a server to make requests of it. Servers respond to their clients by acting on each request and returning results. One server supports many clients, and multiple servers can be networked together in a server pool to handle increased processing loads as the number of clients grows.

A client computer and a server computer are usually two separate units of hardware, each customized for their designed purpose. For example, a web client works best with a large screen display, while a web server doesn't need any display at all and can be located anywhere in the world. In some cases, however, a given device can function both as a client and a server for the same application. Additionally, a device that is a server for one application can simultaneously act as a client to other servers for different applications.

Some of the most popular applications on the internet follow the client-server model, including email, FTP, and web services. Each of these clients features a user interface — either graphic or text-based — and a client application that allows the user to connect to servers. In the case of email and FTP, users enter a computer name (or sometimes an IP address) into the interface to set up connections to the server.

Local Client-Server Networks

Many home networks use client-server systems on a small scale. Broadband routers, for example, contain DHCP servers that provide IP addresses to the home computers, the DHCP clients. Other types of network servers found in a home include print servers and backup servers.

Client-Server vs. Peer-to-Peer and Other Models

The client-server model of networking was initially developed to share access to database applications among large numbers of users. Compared to the mainframe model, client-server networking has better flexibility because connections can be made on demand as needed rather than being fixed. The client-server model also supports modular applications that can make the job of creating software easier. In the so-called two-tier and three-tier types of client-server systems, software applications are separated into modular components, and each component is installed on clients or servers specialized for that subsystem.

Client-server networking is just one approach to managing network applications. The primary alternative to client-server networking, peer-to-peer networking, treats all devices as having equivalent capability rather than specialized client or server roles. Compared to client-server networks, peer-to-peer networks offer some advantages such as better flexibility in expanding the network to handle a large number of clients. Client-server networks usually offer advantages over peer-to-peer networks as well, such as the ability to manage applications and data in one centralized location.