Development Modules
Client-Service Interface
The client–server model
The client–server model is a distributed application structure that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. Whether a computer is a client, a server, or both, is determined by the nature of the application that requires the service functions.
-
Clients and servers exchange messages in a request–response messaging pattern: The client sends a request, and the server returns a response.
-
To communicate, the computers must have a common language, and they must follow rules so that both the client and the server know what to expect. This is defined in a communications protocol.
-
All client-server protocols operate in the application layer. The application-layer protocol defines the basic patterns of the dialogue.
WCF Callback Service
WCF provides the services to call a client. In which, service will act as client and client will act as service.
-
HTTP protocols are connectionless nature, so it is not supported for callback operation. So BasicHttpBinding and WSHttpBinding cannot be used for this operation.
-
WCF support WSDualHttpBinding for call back operation.
-
All TCP and IPC protocols support Duplex communication.
>
Client-Service Interface - Duplex Service
Duplex services specify a callback contract that the client application must implement in order to provide a callback object for the service to call according to the requirements of the contract.
A duplex service contract is a message exchange pattern in which both endpoints can send messages to the other independently. A duplex service, therefore, can send messages back to the client endpoint, providing event-like behavior. Duplex communication occurs when a client connects to a service and provides the service with a channel on which the service can send messages back to the client.
