C# 4.0 in a Nutshell, 4th Edition

Chapter 15. Networking

The Framework offers a variety of classes in the System.Net.* namespaces for communicating via standard network protocols, such as HTTP, TCP/IP, and FTP. Here’s a summary of the key components:

• A WebClient façade class for simple download/upload operations via HTTP or FTP

• WebRequest and WebResponse classes for more control over client-side HTTP or FTP operations

• HttpListener for writing an HTTP server

• SmtpClient for constructing and sending mail messages via SMTP

• Dns for converting between domain names and addresses

• TcpClient, UdpClient, TcpListener, and Socket classes for direct access to the transport and network layers

The Framework supports primarily Internet-based protocols, although this doesn’t limit applicability to the Internet; protocols such as TCP/IP also dominate local area networks.

The types described in this chapter are defined mostly in the System.Net and System.Net.Sockets namespaces; however, many of the examples also use types in System.IO.

Network Architecture

Figure 15-1 illustrates the .NET networking types and the communication layers in which they reside. Most types reside in the transport layer or application layer. The transport layer defines basic protocols for sending and receiving bytes (TCP and UDP); the application layer defines higher-level protocols designed for specific applications such as retrieving web pages (HTTP), transferring files (FTP), sending mail (SMTP), and converting between domain names and IP addresses (DNS).

Figure 15-1. Network ...