IP Programming Basics

Summary

This chapter tells you how IP is used to transfer data across a network, and how you can watch that data. The WinPcap driver can be used to make any Windows system capable of capturing network packets for monitoring. The WinDump and Analyzer programs display the network data captured from the WinPcap driver.

Once you have captured network packets, you must know how to decode them and thus understand how data is traversing the network. You need a good understanding of the Ethernet and IP layer protocols, along with the higher-level TCP and UDP protocols. Each protocol builds on the previous one, adding more information related to how the data traverses the network. Part of your skill as a C# network programmer will involve understanding the effects of these protocols on your network programs. In transporting data across your network, TCP does not preserve data message boundaries, and UDP does not guarantee message delivery. Both protocols have their pros and cons for network programming.

Finally, the chapter described a few methods that you can use to determine the IP address of Windows systems, using the C# Registry, the Microsoft WMI implementation of WBEM, and DNS classes. The Windows Registry contains network information that can be accessed using the .NET Registry and RegistryKey classes. By querying the Registry for network card information, you can obtain static and dynamic IP addresses of systems your program is running on.

The System.Management namespace contains classes to access the WMI database found in Windows 2000 and later systems (earlier Windows platforms can have the WMI database manually installed). By using standard SQL queries and the ManagementObjectSearcher and ManagementObjectCollection classes, you can determine all the necessary IP address information.

The .NET library also contains standard DNS classes that allow you to query to local hostname and IP addresses. This method will be shown in greater detail in Chapter 4, which explores all of the DNS functions available in the .NET library and shows how to use them in C# network programs