microsoft web services provide the building blocks for constructing distributed Web-based applications in a platform, object model, and multilanguage manner. They are based on open Internet standards, including HTTP and XML. They are used by larger businesses to overcome middleware problems that make it difficult and expensive to connect backend software with front-end client applications over a wide area network (WAN) or the Internet. These problems include high costs of developing and maintaining specialized middleware, difficulty with integration across different platforms, inflexibility, and a need to preserve existing investments in legacy software.

To use Web Services, you must have a Windows-based server, such as Internet Information Services (IIS), that is configured to host and serve Web pages and files over the Internet or a local area network. You also must configure the web server to accept requests from Web clients using the World Wide Web protocol. You must specify the transmission control protocol port on which you want the web server to listen and the name of the folder in which to store the Web site files.

When a Web Service call fails, the callback function named OnWSRequestComplete (shown in Listing 13) is called to handle any data returned from the server. The resulting error object contains a number of strings that identify the problem, and you can retrieve these strings with the WsGetErrorProperty() function by passing in a handle to the error object and the WS_ERROR_PROPERTY_STRING_COUNT constant. This function returns an array of strings with the same zero-based index. microsoft web services