Book Image

Hands-On Network Programming with C

By : Lewis Van Winkle
Book Image

Hands-On Network Programming with C

By: Lewis Van Winkle

Overview of this book

Network programming enables processes to communicate with each other over a computer network, but it is a complex task that requires programming with multiple libraries and protocols. With its support for third-party libraries and structured documentation, C is an ideal language to write network programs. Complete with step-by-step explanations of essential concepts and practical examples, this C network programming book begins with the fundamentals of Internet Protocol, TCP, and UDP. You’ll explore client-server and peer-to-peer models for information sharing and connectivity with remote computers. The book will also cover HTTP and HTTPS for communicating between your browser and website, and delve into hostname resolution with DNS, which is crucial to the functioning of the modern web. As you advance, you’ll gain insights into asynchronous socket programming and streams, and explore debugging and error handling. Finally, you’ll study network monitoring and implement security best practices. By the end of this book, you’ll have experience of working with client-server applications and be able to implement new network programs in C. The code in this book is compatible with the older C99 version as well as the latest C18 and C++17 standards. You’ll work with robust, reliable, and secure code that is portable across operating systems, including Winsock sockets for Windows and POSIX sockets for Linux and macOS.
Table of Contents (26 chapters)
Title Page
About Packt

How hostname resolution works

The DNS is used to assign names to computers and systems connected to the internet. Similar to how a phone book can be used to link a phone number to a name, the DNS allows us to link a hostname to an IP address.

When your program needs to connect to a remote computer, such as, it first needs to find the IP address for In this book so far, we have been using the built-in getaddrinfo() function for this purpose. When you call getaddrinfo(), your operating system goes through a number of steps to resolve the domain name.

First, your operating system checks whether it already knows the IP address for If you have used that hostname recently, the OS is allowed to remember it in a local cache for a time. This time is referred to as time-to-live (TTL) and is set by the DNS server responsible for the hostname.

If the hostname is not found in the local cache, then your operating system will need to query a DNS server. This...