Summary

We started this chapter by discussing the general problem of finding web services that we might want to use. To address the problem, we looked at UDDI, and how organizations can use it to find and register web services. We then stepped through the use of UDDI, using Microsoft's UDDI node, to demonstrate its typical use in discovering SOAP Web services.

After discussing the uses of UDDI, we mentioned that there still needs to be a way of describing the capabilities of web services, such as the protocols they support as well as the data types and XML schemas that may be used. To address this problem, we introduced WSDL.

Thanks to WSDL, we can build software based on the XML blueprint of a web service. We discussed the use of both Visual Studio .NET, and the wsdl.exe command-line tool to create this proxy software. After creating proxies with both of these tools, we demonstrated how to use them and stepped through some common scenarios, including setting the timeout value and using HTTP cookies.

Following our discussion of building .NET proxies for web services, we went on to HTML screen-scraping and how we could use a simple WSDL document and the support for regular expressions in .NET to easily turn any web site into a web service.

Next , we saw several design decisions for web services. We looked at handling exceptions and how to use SOAP headers to send out-of- band data (that is, data that doesn't belong as part of the body of the SOAP message).

Finally, we discussed security “both the options provided by ASP.NET, such as Forms or Windows authentication, and some custom security and encryption options that can be implemented.

That completes our coverage of web services. In the next chapter we'll turn our attention to Mobile Controls.