WCF (Basics..for building effective Services)
WCF: Windows Communication Foundation
It includes a collection of .NET distributed technologies that have existed for long , but never got grouped under one name.
WCF can be considered as collection of the following technologies.
- Web Services(ASMX)
- NET Enterprise Services
- MSMQ
- .NET Remoting
Code written in WCF can interact across components, applications and systems.
WCF is in accordance with SOA (Service Oriented Architecture).
Following Sections provide the details of these ABCs.
Addresses
In WCF, every service has a unique address. The address provides two important elements
A) Location of the service.
B) Transport protocol or transport schema used to communicate with the service.
The location indicates the name of the target machine, site, or network; a communication port, pipe, or queue; and an optional specific path or URI.
WCF supports the following transport schemas:
A) HTTP
B) TCP
C) Peer network
D) IPC (Inter-Process Communication over named pipes)
E) MSMQ
Addresses have the following format:
[base address]/[URI]
(Note: URI is optional and can be omitted, however when it is present it gets merged with the base address to provide the final address, where the service can be located).
base address format:
[transport]:// [machine or domain][:optional port]
Following section is meant only to make you familiar with the various formats thatare used with specific type of transport protocol.
It can be skipped if desired.
Using different available address formats.
TCP Addresses
TCP addresses use net.tcp for the transport and generally uses a port:
net.tcp ://{ machine or domain}/ServiceName
e.g. Net.tcp//localhost/PService
(Note: If a port number is not specified, Port 808 is used as default)
HTTP Addresses
HTTP addresses use httpfor transport, and https can be used if secure transport is required.
e.g.http://localhost:8001
When the port number is not mentioned, it defaults to 80.
IPC Addresses
IPC addresses use net.pipe for transport.
Note: If a service uses this (i.e. named pipes, it can accept call only from thesame machine).
e.g. net.pipe://localhost/PrPipe
MSMQ Addresses
MSMQ addresses use net.msmq for transport
When private queues are used, queue type needs to be mentioned and is omittedfor public queues:
net.msmq://localhost/private/PService (using private queue)
net.msmq://localhost/PService (usingPublic Queue)
Peer Network Address
Peer network addresses use net.p2p for transport peer network name, path and port needs to be specified.....
Bindings
The Standard Bindings Following 9 types of Bindings are defined for WCF:
Basic Binding
BasicHttpBinding class provides this type of binding.
It exposes a WCF service as a legacy ASMX web service.
This binding is extremely useful when the intent is to design a WCF service that should provide backward compatibility with WebServices.
TCP binding
NetTcpBinding class provides this type of binding.
It uses TCP for cross-machine communication on the intranet.
It supports a variety of features, including reliability, transactions, andsecurity, and is optimized for WCF-to-WCF communication.
Restriction: It requires both the client and the service to use WCF.
Peer network binding
NetPeerTcpBinding class provides this type of binding and uses peer networking as a transport. The peer network-enabled client and services all subscribe to the same grid and broadcast messages to it....
IPC binding
NetNamedPipeBinding class provides this type of binding and uses named pipes as a transport for same-machine communication. It is the most secure binding as it cannot accept calls from outside the machine and it supports a number of features similar to the TCP binding.
Web Service (WS) binding
WSHttpBinding class provides this type of binding, and uses HTTP or HTTPS for transport....
Federated WS binding
WSFederationHttpBinding class provides this type of binding, this is a specializationof the WS binding, offering support for federated security......
Duplex WS binding
WSDualHttpBinding class provides this type of binding. It is similar to the WS binding except it also supports bi-directional communication from the service to the client.
MSMQ binding
NetMsmqBinding class provides this type of binding and uses MSMQ for transport and is suitable for disconnected queued calls...
MSMQ integration binding
MsmqIntegrationBinding class provides this type of binding and converts WCF messages to and from MSMQ messages. This is most suitable for usage when Service legacy MSMQ clients interoperability is critical.
Message Transfer Patterns
WCF use the following three messaging patterns:
- Simplex,
- Duplex
- Request-Reply.
Simplex communication is commonly referred to as one-way communication. This approachis used when asynchronous write-only services are required. It simply means if onlyone directional (client to Service) communication is required, use this pattern.
Duplex communication provides true asynchronous two-way communications. (using callback operations).
In simplex and duplex communication, the consumer is not locked into waiting for a reply.
Request-Reply: General enough not to provide any details
Defining Bindings is one the most critical stages in WCF Service development. Service development.
Correct type of binding can save a lot of time and effort need to build an effective service.
As an effort to make you comfortable in Service development below is the checklist that needs to be referred before finalizing bindings for your service.
Interoperability Level:
Make sure if communication will only be in a .NET to .NET scenario,or legacy ASMX service, or if it is to be used by a consumer that adheres to the WS* specifications.
Encoding:
Select correct type of encoding, from among
Text
Message TransmissionOptimization Mechanism (MTOM)
Binary.
Transport Protocols
Select from transport options TCP, HTTP, Named Pipe, and MSMQ.
Messaging patterns : simplex, duplex, and request-reply.
Security Considerations: WinTransactions and reliable sessions.
Contracts:
The contract is a platform-neutral and standard way of describing what the service does.
WCF defines four types of contracts.
Service contracts
Describe which operations the client can perform on the service.
Data contracts
Define which data types are passed to and from the service.
Fault contracts
Define which errors are raised by the service, and how the service hand Allow the service to interact directly with messages. Message contracts can be typed or untyped.
Service Type Support e.g. Message contract The following are the three types of services that can be written with WCF.
- Typed Services: These services use exact parameterization(passingthe required parameters in the correct order, format and type) when calling a servicemethod and respond with a well-defined type(as expected by the caller).
- Un-Typed Services: XML is the core of this type as it is used totransport the input parameters and the response output is also in XML. These servicesare the most flexible, but provide very little value back to the consumer.
- Typed Message Services: A custom type is defined that will containthe required input parameters and one more type that will wrap up the output parameters.
This approach is generallyknown as Request Object / Response Object, since these are the types of objects that are result ofthese types of services.
This tutorial is just meant as a base for understanding the nitty-gritties of WCF.
Next tutorial will cover the detailed implementation of the theoretical sections discussed here.
Till then, Happy Coding...
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