A simple HTTPS client

To bring the concepts of this chapter together, we build a simple HTTPS client. This client can connect to a given HTTPS web server and request the root document /. 

Our program begins by including the needed chapter header, defining main(), and initializing Winsock as shown here:

/*https_simple.c*/

#include "chap09.h"

int main(int argc, char *argv[]) {

#if defined(_WIN32)
    WSADATA d;
    if (WSAStartup(MAKEWORD(2, 2), &d)) {
        fprintf(stderr, "Failed to initialize.\n");
        return 1;
    }
#endif

We then initialize the OpenSSL library with the following code:

   /*https_simple.c continued*/

    SSL_library_init();
    OpenSSL_add_all_algorithms();
    SSL_load_error_strings();

The SSL_load_error_strings() function call is optional, but it's very useful if we run into problems.

We can also create an OpenSSL context...