clientserveur

Client-server, or client–server architecture, is a distributed computing model in which client devices request resources or services from centralized server software over a network. Clients are user interfaces such as web browsers or mobile apps; servers host resources or services, such as web pages, databases, or files, and respond to requests.

In typical deployments, a server serves many clients. The architecture can be two-tier (one server, many clients) or multi-tier (three-tier or more), separating concerns among clients, application logic, and data stores. Communication follows a request–response pattern over protocols such as HTTP/HTTPS, or via RPC frameworks. APIs using REST or SOAP are common ways for applications to exchange data.

History and scope: The client–server model emerged with early time-sharing and became dominant with the rise of the web. In French, the term is commonly written client-serveur. Modern implementations often use web servers, application servers, and database servers, and may employ microservices or service-oriented architectures to distribute functionality across multiple servers.

Examples and use cases: web browsers and web servers, email clients and mail servers (SMTP/IMAP/POP), and database clients with database servers. File sharing services and authentication services also rely on client–server interactions.

Advantages include centralized resource management, scalability, and easier security enforcement. Disadvantages include network dependency, potential bottlenecks, and the risk of a single point of failure in simple two-tier setups.

Security and design considerations emphasize authentication, authorization, encryption (TLS), and input validation. Stateless protocols like HTTP aid scalability, while stateful components may be needed for certain sessions; performance can be improved with caching and load balancing.