In computing, "server" dates at least to RFC 5 (1969),[5] one of the earliest documents describing ARPANET (the predecessor of Internet), and is contrasted with "user", distinguishing two types of host: "server-host" and "user-host".In the publish-subscribe pattern, clients register with a pub-sub server, subscribing to specified types of messages; this initial registration may be done by request-response.There are exceptions that do not use dedicated servers; for example, peer-to-peer file sharing and some implementations of telephony (e.g. pre-Microsoft Skype).Since servers are usually accessed over a network, many run unattended without a computer monitor or input device, audio hardware and USB interfaces.Large traditional single servers would need to be run for long periods without interruption.Mission-critical enterprise servers would be very fault tolerant and use specialized hardware with low failure rates in order to maximize uptime.They will often be able to be configured, powered up and down, or rebooted remotely, using out-of-band management, typically based on IPMI.Modern data centers are now often built of very large clusters of much simpler servers,[15] and there is a collaborative effort, Open Compute Project around this concept.A class of small specialist servers called network appliances are generally at the low end of the scale, often being smaller than common desktop computers.[17] The main beneficiaries of so-called "server on the go" technology include network managers, software or database developers, training centers, military personnel, law enforcement, forensics, emergency relief groups, and service organizations.[21][needs update] One estimate is that total energy consumption for information and communications technology saves more than 5 times its carbon footprint[22] in the rest of the economy by increasing efficiency.
The first
WWW
server is located at
CERN
with its original sticker that says: "This machine is a server. DO NOT POWER IT DOWN!!"
A network based on the
client–server model
where multiple individual
clients
request services and resources from centralized servers
A
rack-mountable
server with the top cover removed to reveal internal components
Sun's
Cobalt Qube
3; a computer
server appliance
(2002); running Cobalt Linux (a customized version of Red Hat Linux, using the 2.2 Linux kernel), complete with the Apache web server.