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

HTTPS server with OpenSSL

Let's go over some basics of using the OpenSSL library in server applications before beginning a concrete example.

Before OpenSSL can be used, it must be initialized. The following code initializes the OpenSSL library, loads the requisite encryption algorithms, and loads useful error strings:


Refer to the previous Chapter 9, Loading Secure Web Pages with HTTPS and OpenSSL, for more information.

Our server also needs to create an SSL context object. This object works as a sort of factory from which we can create TLS/SSL connections.

The following code creates the SSL_CTX object:

SSL_CTX *ctx = SSL_CTX_new(TLS_server_method());
if (!ctx) {
    fprintf(stderr, "SSL_CTX_new() failed.\n");
    return 1;

If you're using an older version of OpenSSL, you may need to replace TLS_server_method() with TLSv1_2_server_method() in the preceding code. However, a better solution is to upgrade to a newer OpenSSL...