Web Services

A web service is an application that exposes a Web accesible API. That means you can invoke the application programmatically over the web. Applications invoking this Web Service are referred to as clients.
An XML web service is a .NET component that replies to HTTP requests that are formatted using the SOAP syntax.
Web services allow a degree of interoperability among applications over the Internet.
XML web services are just ASP.NET applications that intercept requests for .asmx files.


These are application components
They communicate using open protocols
They are self contained and self describing
They can be discovered using UDDI
A basic web service is XML plus HTTP



You construct a web page that takes parameters in the query string and returns the relevant data. The client then sends an HTTP Get request with the appropriate URL.


These allow access to software components through standard web protocols such as HTTP and SMTP.
Web services allow us to use the Internet and XML to create software components that communicate with each other regardless of language or platform.


XML - This is used to structure the data
SOAP - This is used to transfer the data
This stands for Simple Object Access Protocol.
SOAP is an XML based protocol that allows applications to exchange information over http.
It is a communication protocol
It is platform independent
It is based on XML, HTTP and SMTP
It is language independent


WSDL - This is used to describe the web service, the description of the methods provided (Web Service Description Language)
UDDI - This is used to get a list of services available. This is a directory service where companies can register and search for web services. This stands for Universal Description, Discovery and Integration.
SMTP -


Relevant Namespaces

System.Web.Services 
System.Web.Services.Protocols
System.Net
System.Threading
System.Web.Security
System.IO



references.vb

This file holds the proxy class for the client side component of the web service and is generated automatically.



Different types of web interaction




Web Queries



Discovery File (.disco)

This provides information to help browsers determine the URLs at any websites which web services are available.




Async Calls

When you fire off multiple async web calls maintain an arraylist of all the calls we are waiting for - need a consistent naming convention
May be nicer to have an event that fires when they have all been returned.



Proxy Class



Fiddler

This is free Microsoft Web Services debugging tool




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