I am working on an article for the same. the article is not complete but i am sending you the text from the draft copy of it:
The major limitation with web services is that the comunication can happen over HTTP only. Second limitation with web services is that it provide singlex communication and there is no way to have half duplex or full duplex communication using web services.
Windows Communication Foundation(WCF) comes to the rescue when we find ourself not able to achive what we want to achieve using web services i.e. other protocols support and even duplex communication. With WCF we can define our service once and then configure it in such a way that it can be used via HTTP, TCP, IPC and even Message queues. We can consume web services using server side scripts (ASP.NET), Javascript Object Notations(JSON) and even REST(Representational State Transfer)
Following table illustrates the differences between a web service and WCF service
Web Service | WCF Service |
Coomunication can happen over HTTP only | Communication can happen over HTTP, TCP, IPC or even MSMQ |
Only Singlex and request-response communication is possible | It can be configured to have singlex, request-response or even full duplex communication |
They work in an stateless fasion over HTTP and are hosted inside a web server like IIS | These can be hosted in many ways inside IIS, inside a Windows service or even self hosted.
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Note: Apart from these differences there are other differences related to instance management,sessions and data representation and serialization.
P.S.: I will post the complete article on 10th of June as it will need some work to complete it.