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

Implementing a web client

We will now implement an HTTP web client. This client takes as input a URL. It then attempts to connect to the host and retrieve the resource given by the URL. The program displays the HTTP headers that are sent and received, and it attempts to parse out the requested resource content from the HTTP response.

Our program begins by including the chapter header, chap06.h:


#include "chap06.h"

We then define a constant, TIMEOUT. Later in our program, if an HTTP response is taking more than TIMEOUT seconds to complete, then our program abandons the request. You can define TIMEOUT as you like, but we give it a value of five seconds here:

/*web_get.c continued*/

#define TIMEOUT 5.0

Now, please include the entire parse_url() function as given in the previous section. Our client needs parse_url() to find the hostname, port number, and document path from a given URL.

Another helper function is used to format and send the HTTP request. We call it send_request(), and...