post json data through https in c - c

Question

I found the following code snippet and did few changes to post json data to a re_url . But it is showing error failed connection ...the server listens on the 8888 port for json data.
#include <stdio.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/bio.h>
#define APIKEY "YOUR_API_KEY"
#define HOST "https://YOUR_WEB_SERVER_URI"
#define PORT "8888"
char *s = "somejson";
int main() {
//
// Initialize the variables
//
BIO* bio;
SSL* ssl;
SSL_CTX* ctx;
//
// Registers the SSL/TLS ciphers and digests.
//
// Basically start the security layer.
//
SSL_library_init();
//
// Creates a new SSL_CTX object as a framework to establish TLS/SSL
// or DTLS enabled connections
//
ctx = SSL_CTX_new(SSLv23_client_method());
//
// -> Error check
//
if (ctx == NULL)
{
printf("Ctx is null\n");
}
//
// Creates a new BIO chain consisting of an SSL BIO
//
bio = BIO_new_ssl_connect(ctx);
//
// Use the variable from the beginning of the file to create a
// string that contains the URL to the site that you want to connect
// to while also specifying the port.
//
BIO_set_conn_hostname(bio, HOST ":" PORT);
//
// Attempts to connect the supplied BIO
//
if(BIO_do_connect(bio) <= 0)
{
printf("Failed connection\n");
return 1;
}
else
{
printf("Connected\n");
}
//
// The bare minimum to make a HTTP request.
//
char* write_buf = "POST / HTTP/1.1\r\n"
"Host: " HOST "\r\n"
"Authorization: Basic " APIKEY "\r\n"
"Connection: close\r\n"
"\r\n";
//
// Attempts to write len bytes from buf to BIO
//
if(BIO_write(bio, write_buf, strlen(write_buf)) <= 0)
{
//
// Handle failed writes here
//
if(!BIO_should_retry(bio))
{
// Not worth implementing, but worth knowing.
}
//
// -> Let us know about the failed writes
//
printf("Failed write\n");
}
//
// Variables used to read the response from the server
//
int size;
char buf[1024];
//
// Read the response message
//
for(;;)
{
//
// Get chunks of the response 1023 at the time.
//
size = BIO_read(bio, buf, 1023);
//
// If no more data, then exit the loop
//
if(size <= 0)
{
break;
}
//
// Terminate the string with a 0, to let know C when the string
// ends.
//
buf[size] = 0;
//
// -> Print out the response
//
printf("%s", buf);
}
//
// Clean after ourselves
//
BIO_free_all(bio);
SSL_CTX_free(ctx);
return 0;
}
The code above will explain in details how to establish a TLS connection with a remote server.
Important note: this code doesn't check if the public key was signed by a valid authority. Meaning I don't use root certificates for validation. Don't forget to implement this check otherwise you won't know if you are connecting the right website
When it comes to the request itself. It is nothing more then writing the HTTP request by hand.
You can also find under this link an explanation how to instal openSSL in your system, and how to compile the code so it uses the secure library.

Answer 1

From BIO_set_conn_hostname:
BIO_set_conn_hostname() uses the string name to set the hostname. The
hostname can be an IP address. The hostname can also include the port
in the form hostname:port . It is also acceptable to use the form
"hostname/any/other/path" or "hostname:port/any/other/path".
You do not provide a valid host name:
#define HOST "https://YOUR_WEB_SERVER_URI"
...
// Use the variable from the beginning of the file to create a
// string that contains the URL to the site that you want to connect
// to while also specifying the port.
BIO_set_conn_hostname(bio, HOST ":" PORT);
The comment correctly refers to a URL but instead you provide a URI which is most probably wrong.
If you replace YOUR_WEB... with the real host name, it is still a URI and not a host name.
Try to remove the "https://" part and only provide the host name.