Web service is a web API (collections of operations) to access the requested remote services via HTTP. Web service became very successful in the market becuase of it's platform independency. i.e.; A web service can be developed in Java and the client who access the service can be in any other language like .NET.

How does web service platform independent?

Web service provider and web service client work based on the XML trasmission. i.e.; each request will be sent to the provider as an XML and response would be recieved as an XML. So, any language which can understand and parse the XML can be used for web services.

How the XML can be understandable by provider and client?

Web service provider will create an XML file called WSDL (Web service description language) in order to develop a service. WSDL is a common standard defined by Microsoft and supported by other companies Sun, IBM, Oracle etc. WSDL contains the prototypes for all the operations. WSDL is publicly available file for the clients to invoke the services

Web service client needs to access the WSDL in order to invoke web service provider operations remotely.

So, web service provider and client will have a standard defined in the form of WSDL to communicate each other. Communication will happen by exchanging the information thru SOAP protocol.

In my future posts, I'll cover how to create web service provider using Java and web service handlers to modify the XML request and response.