Network Programming in .NET: With C# and Visual Basic .NET
Addressing real-world issues facing professional developers, the purpose of this book is to provide tools to design and implement network-orientated applications in .NET.
TABLE OF CONTENTS Network Programming in .NET: With C# and Visual Basic .NET
Chapter 3: Working with Sockets
3.1 Introduction
This chapter explains the most important aspect of network programming, the socket. It is essential to fully understand how to use sockets in .NET before proceeding to the following chapters. Examples in this chapter will enable the user to send files and messages over the Internet, using simple network applications.
Two socket-level protocols are described in this chapter. Both protocols are demonstrated as a pair of applications one client, one server. This follows the classic client/server model, which is prevalent in most distributed applications. The chapter follows this structure, describing the client first, followed immediately by an implementation of the server.
3.2 What is a Socket?
A socket is an object that represents a low-level access point to the IP stack. This socket can be open or closed or one of a set number of intermediate states. A socket can send and receive data down this connection. Data is generally sent in blocks of a few kilobytes at a time for efficiency; each of these blocks is called a packet.
All packets that travel on the Internet must use the Internet protocol. This means that the source IP address, destination address must be included in the packet. Most packets also contain a port number. A port is simply a number between 1 and 65,535 that is used to differentiate higher protocols, such as email or FTP (Table 3.1). Ports are important when it comes to programming your own network applications because no two applications can use the same...
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