Although the terms “client” and “server” are among the most frequently used in the IT world, they are often applied in very different contexts:
In general, they refer to the role assumed by two partners during communication: the client requests a service, while the server provides the service.
The clients of a UTM application can be:
terminals or terminal emulations
UPIC clients (see "Clients with the UPIC carrier system")
OpenCPIC clients (see "Clients with the OpenCPIC carrier system")
transport system applications (see "Communicating with transport system applications")
- HTTP-Clients (siehe "Communicating with HTTP-Clients")
UPIC clients and OpenCPIC clients are also referred to as openUTM clients. But the terms “client” and “server” can also refer to entire applications:
UTM applications are known as server applications, since they normally act as servers during communication, i.e. they provide services. However, when fulfilling certain service requests, they in turn request other services, i.e. they act as clients. Unlike server applications which can assume either role, client applications can only function as clients during communication. They are generally responsible for presentation tasks and form the front-end to the users.
Communication between two server applications is known as server-to-server communication or peer-to-peer communication. This conveys that fact that the communication process involves two partners of equal ranking, although this form of communication can of course distinguish between the client and server roles. This type of interaction is also known as distributed processing.
The terms “client” and “server” frequently refer to hardware. Client PCs or client workstations are systems on which client software has been installed. Powerful systems that are particularly suitable for server applications are often called “servers”.