Professional C# 2005

Chapter 35. Accessing the Internet

Chapters 26 through 28 discuss how you can use C# to write powerful, efficient, and dynamic Web pages using ASP.NET and XML Web services. For the most part, the clients accessing ASP.NET pages will be users running Internet Explorer or other Web browsers such as Opera or FireFox. However, you might want to add Web-browsing features to your own application, or need your applications to programmatically obtain information from a Web site. In this latter case, it is usually better for the site to implement a Web service. However, if you are accessing public Internet sites you might not have any control over how the site is implemented.

This chapter covers facilities provided through the .NET base classes for using various network protocols, particularly HTTP and TCP, to access networks and the Internet as a client. In particular, this chapter covers:

• Downloading files from the World Wide Web

• Using the new Web Browser control in a Windows Forms application

• Manipulating IP addresses and performing DNS lookups

• Socket programming with TCP, UDP, and socket classes

The two namespaces of most interest for networking are the System.Net and the System.Net.Sockets namespaces. The System.Net namespace is generally concerned with higher-level operations, for example, downloading and uploading files, and making Web requests using HTTP and other protocols, whereas System.Net.Sockets contains classes to perform lower-level operations. You will find these classes more ...