WCF

The Windows Communication Foundation (or WCF) is an application programming interface in the .NET Framework for building connected, service-oriented applications.

The Architecture
WCF is designed in accordance with service oriented architecture principles to support distributed computing where services are consumed by consumers. Clients can consume multiple services and services can be consumed by multiple clients. Services are loosely coupled to each other. Services typically have a WSDL interface which any WCF client can use to consume the service, irrespective of which platform the service is hosted on. WCF implements many advanced web services (WS) standards such as WS-Addressing, WS-ReliableMessaging and WS-Security.

Services
A WCF service is composed of three parts — a Service class that implements the service to be provided, a host environment to host the service, and one or more endpoints to which clients will connect. All communication with the WCF service happens via the endpoints. The endpoints specify a Contract that defines which methods of the Service class will be accessible via the endpoint; each endpoint may expose a different set of methods. The endpoints also define a binding that specifies how a client will communicate with the service and the address where the endpoint is hosted.
In Windows Vista, Windows Server 2008 and Windows 7 (operating systems that include IIS 7), Windows Activation Services can be used to host the WCF service. Otherwise the WCF service can be hosted in IIS, or it can be self-hosted in any process by using the ServiceHost class, which is provided by WCF. A self-hosted WCF service might be provided by a console-based application, a Windows Forms application, or a Windows service (the Windows counterpart to a daemon), for example.

Adoption
Microsoft partners are supporting WCF. SAP delivers add-ins to the Visual Studio development environment that can generate WCF client-side proxies that connect to SAP Enterprise systems. IBM is producing a WCF Channel for MQ. Microsoft has also delivered The WCF Line of Business Adapter SDK to enable developers to create WCF-based communication connectivity to virtually any external system. The WCF LOB Adapter SDK is what enables JNBridge, for example, to build the JMS Adapter for .NET.