1. A program which provides some service to other (client) programs. The connection between client and server is normally by means of message passing, often over a network, and uses some protocol to encode the client's requests and the server's responses. The server may run continuously (as a daemon), waiting for requests to arrive or it may be invoked by some higher level daemon which controls a number of specific servers (inetd on Unix). There are many servers associated with the Internet, such as those for HTTP, Network File System, {Network Information Service} (NIS), Domain Name System (DNS), FTP, news, finger, Network Time Protocol. On Unix, a long list can be found in /etc/services or in the NIS database "services". See client-server. 2. A computer which provides some service for other computers connected to it via a network. The most common example is a file server which has a local disk and services requests from remote clients to read and write files on that disk, often using Sun's Network File System (NFS) protocol or Novell Netware on PCs. Another common example is a {web server}. [Jargon File] (2003-12-29)

(servers)

In computing, a server is a piece of computer hardware or software (computer program) that provides functionality for other programs or devices, called "clients". This architecture is called the client–server model.

server

HTTP server

A web server is computer software and underlying hardware that accepts requests via HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, commonly a web browser or web crawler, initiates communication by making a request for a web page or other resource using HTTP, and the server responds with the content of that resource or an error message.

<programming> A common form of distributed system in which software is split between server tasks and client tasks. A client sends requests to a server, according to some protocol, asking for information or action, and the server responds. This is analogous to a customer (client) who sends an order (request) on an order form to a supplier (server) who despatches the goods and an invoice (response). The order form and invoice are part of the "protocol" used to communicate in this case. There may be either one centralised server or several distributed ones. This model allows clients and servers to be placed independently on nodes in a network, possibly on different hardware and operating systems appropriate to their function, e.g. fast server/cheap client. Examples are the name-server/name-resolver relationship in DNS, the file-server/file-client relationship in NFS and the screen server/client application split in the {X Window System}. Usenet newsgroup: news:comp.client-server. ["The Essential Client/Server Survival Guide", 2nd edition, 1996]. (1998-01-25)

Messages Server is a component of OS X Server from Apple Inc. It was first introduced as iChat Server with the release of Mac OS X Server 10.