Client-server

Clients characteristics

Always initiates requests to servers.
Waits for replies.
Receives replies.
Usually connects to a small number of servers at one time.
Usually interacts directly with end-users using any user interface such as graphical user interface.

Always wait for a request from one of the clients.
Serves clients' requests then replies to the clients with the requested data.
A server may communicate with other servers in order to serve a client request.
If additional information is required to process a request (or security is implemented), a server may request additional data (passwords) from a client before processing a request.
End users typically do not interact directly with a server, but use a client.

Specific types of clients include: web browsers, E-mail clients, and online chat clients.
Specific types of servers include: web servers, FTP servers, database servers, E-mail servers, file servers, print servers. Most web services are also types of servers.