clientserver

The client-server model is a distributed computing architecture in which networked clients request services or resources from centralized servers. In everyday use, a web browser (client) requests web pages from a web server.

Clients and servers run on separate machines connected by a network, and communication follows a request-response pattern. Protocols such as HTTP over TCP/IP govern these exchanges, and while HTTP is stateless, servers often manage state with sessions or tokens.

Server roles include web servers, application servers, database servers, file servers, and mail servers. Clients include browsers, mobile apps, and other software that consumes the server’s services.

Architectures range from two-tier setups to three-tier or multi-tier designs that separate presentation, logic, and data. Scaling is supported by load balancing, server clustering, and caching; security relies on encryption (TLS/SSL), strong authentication, and access controls.

The model has its roots in timesharing and mainframe-era computing and matured during the 1980s and 1990s with the rise of networked personal computers.