Client-server Protocol

Client-server Protocol

The client–server model is an approach to network architecture developed at Xerox PARC during the 1970s. Email, the World Wide Web, and network printing all apply the client–server model.

The model assigns one of two roles to the computers in a network: Client or server. A server is a computer system that selectively shares its resources; a client is a computer or computer program that initiates contact with a server in order to make use of a resource. Data, CPUs, printers, and data storage devices are all examples of resources.

This sharing of computer resources is called time-sharing, because it allows multiple people to use a computer (in this case, the server) at the same time. Because a computer does a limited amount of work at any moment, a time-sharing system must quickly prioritize its tasks to accommodate the clients.

Whether a computer is a client, a server, or both, it can serve multiple functions. For example, a single computer can run web server software and file server software at the same time to serve different data to clients making different kinds of requests. Client software can also communicate with server software on the same computer. Communication between servers, such as to synchronize data, is sometimes called inter-server or server-to-server communication.

All client–server protocols are application layer protocols.