Chapter 10: Extending the Lines of Communication

Overview

Web services exist to extend the capabilities a website offers to programs and ASP.NET pages you create. In this chapter, you will first create web services that programs can use to send e-mail messages and faxes. As you will learn, by using a web service to offer these services, you make it easy to integrate security (encrypted messages based on public keys) and to log the e-mail messages that you must send from a remote location.

Although most computer users now send e-mail messages as opposed to faxes, many people still prefer faxes. Sometimes the recipient has easy access to a fax machine, but not to e-mail. And many people feel that legal and other “permanent” documents should be sent via fax. This chapter introduces the fax capabilities offered by the website eFax.com, which turns faxes into e-mail and vice versa for seamless transmission of documents. Using the web services this chapter presents, your programs can e-mail documents to the site, which the site, in turn, will fax to the recipients your programs specify.

The chapter will also present a Chat web service that you can use to implement instant-messaging and group-chat applications. Although you might never need to implement a similar web service, the issues you must consider with respect to synchronizing remote data access are applicable to a wide range of applications. The Chat web service shares the buffer containing the current messages among all programs that connect to the web service. As you will learn, the web service locks the buffer each time a user accesses the messages and then unlocks the buffer after the user completes her operations. By locking and unlocking the buffer in this way, the web service prevents one program from changing the buffer’s contents while another program is also using the data.