Server

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A server is a computer program that delivers a service to clients. The server and client programs are usually, but not necessarily, running on different computers communicating over a network.

Examples

A web server delivers a web page when requested by a web browser (called client in this context). The predefined way a server and client communicates is called a protocol. For instance, HTTP is the protocol used between a browser and a web server. Among the many services provided by the Internet servers are:

• World Wide Web
• the domain name system
• e-mail
• FTP file transfer
• chat and instant messaging
• voice communication
• streaming audio and video
• online gaming

Virtually every action taken by an ordinary Internet user requires one or more interactions with one or more servers.

There are also technologies that operate on an inter-server level. Other services do not use dedicated servers; for example peer-to-peer file sharing, some implementations of telephony (e.g. Skype), and supplying television programs to several users (e.g. Kontiki).

Servers in daily life

Any computer or device serving out applications or services can technically be called a server. In an office or enterprise environment, the network server is easy to identify. A DSL/Cable modem router qualifies as a server because it provides a computer with application services like IP address assignment (via DHCP), NAT, and a firewall that helps protect a computer from external threats. iTunes software implements a music server to stream music between computers. Many home users create shared folders and printers. Another example are the many servers that are used for hosting online games such as Everquest, Final Fantasy XI, Counter-Strike and Eve Online.

References

Wikimedia Commons has media related to: Servers

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