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How to Make an Https Request In C?

5 minutes read

To make an HTTPS request in C, you can use the libcurl library which provides an easy-to-use interface for making HTTP requests.


First, you need to include the libcurl header file in your C program. Then, you can create a CURL object using the curl_easy_init() function.


Next, you can set the URL of the request using the curl_easy_setopt() function with the CURLOPT_URL option. You can also set other options such as setting the request type (GET or POST) and adding headers using the curl_easy_setopt() function.


To make the actual request, you can call the curl_easy_perform() function on the CURL object. This will send the request to the server and wait for a response.


After receiving the response, you can read the data using the curl_easy_getinfo() function and process it as needed.


Finally, don't forget to clean up resources by calling curl_easy_cleanup() to free memory allocated for the CURL object.


Overall, using the libcurl library is a straightforward way to make HTTPS requests in C and handle responses efficiently.


How to make an https request in c with custom headers?

To make an HTTPS request in C with custom headers, you can use the libcurl library. Here is an example code snippet that demonstrates how to make an HTTPS request with custom headers using libcurl:

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#include <stdio.h>
#include <curl/curl.h>

int main() {
    CURL *curl;
    CURLcode res;
    
    curl = curl_easy_init();
    if(curl) {
        // Set the URL
        curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
        
        // Set custom headers
        struct curl_slist *headers = NULL;
        headers = curl_slist_append(headers, "Content-Type: application/json");
        headers = curl_slist_append(headers, "Authorization: Bearer your_access_token_here");
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        
        // Perform the request
        res = curl_easy_perform(curl);
        
        // Clean up
        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
        
        if(res != CURLE_OK) {
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        }
    }
    
    return 0;
}


In this code snippet, we first initialize a CURL handle using curl_easy_init(). We then set the URL for the request using curl_easy_setopt() with the CURLOPT_URL option. Next, we set custom headers using the curl_slist struct and curl_slist_append() function, and then set them for the request using curl_easy_setopt() with the CURLOPT_HTTPHEADER option.


We then perform the request using curl_easy_perform(). If the request is successful, the response data will be returned. Finally, we clean up by freeing the curl_slist headers and cleaning up the CURL handle.


Remember to link your code with the libcurl library when compiling:

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gcc -o myprogram myprogram.c -lcurl



What is certificate validation in the context of making https requests in c?

Certificate validation in the context of making HTTPS requests in C involves verifying the authenticity and validity of the SSL/TLS certificate presented by the server during the SSL/TLS handshake process. This validation process is crucial for ensuring secure and encrypted communication between the client and the server.


In C, certificate validation typically involves checking the certificate chain, verifying the issuer signature, expiration date, and ensuring that the certificate is issued by a trusted Certificate Authority (CA). If any of these checks fail, the connection may be considered insecure, and the client should not proceed with the communication.


To perform certificate validation in C, developers can use libraries such as OpenSSL, GnuTLS, or mbedTLS. These libraries provide functions and APIs for handling certificate validation, allowing developers to implement secure HTTPS communication in their C applications.


What is the purpose of referrer header in making https requests in c?

The purpose of the referrer header in making HTTPS requests in C is to provide information about the URL of the webpage that referred the user to the current webpage. By including the referrer header in an HTTPS request, the server receiving the request can track where the user came from and use that information for analytics or other purposes. This can help website owners understand their traffic sources and optimize their website accordingly.


How to make an https request in c using OpenSSL?

To make an HTTPS request in C using OpenSSL, you can follow the steps outlined below:

  1. Include the necessary OpenSSL libraries at the top of your C file:
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#include <openssl/bio.h>
#include <openssl/ssl.h>
#include <openssl/err.h>


  1. Initialize the OpenSSL library by calling SSL_library_init() and SSL_load_error_strings():
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SSL_library_init();
SSL_load_error_strings();


  1. Create an SSL_CTX object and set the SSL_METHOD to TLS_client_method:
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SSL_CTX *ctx = SSL_CTX_new(TLS_client_method());


  1. Create a new SSL object and associate it with a BIO object:
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SSL *ssl = SSL_new(ctx);
BIO *bio = BIO_new_ssl_connect(ctx);


  1. Set the hostname and port number for the HTTPS request:
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BIO_set_conn_hostname(bio, "example.com:443");


  1. Connect to the remote server using BIO_do_connect():
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BIO_do_connect(bio);


  1. Send an HTTPS request to the server using BIO_puts():
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const char *request = "GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n";
BIO_puts(bio, request);


  1. Read the response from the server using BIO_read():
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char buf[1024];
int bytes_read;

while ((bytes_read = BIO_read(bio, buf, sizeof(buf))) > 0) {
    printf("%.*s", bytes_read, buf);
}


  1. Optionally, you should also check for any errors that may have occurred during the request:
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if (SSL_get_verify_result(ssl) != X509_V_OK) {
    fprintf(stderr, "SSL certificate verification failed\n");
}

if (ERR_get_error() != 0) {
    ERR_print_errors_fp(stderr);
}


  1. Finally, clean up and free any allocated memory:
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SSL_shutdown(ssl);
SSL_free(ssl);
BIO_free_all(bio);
SSL_CTX_free(ctx);


By following these steps, you should be able to make an HTTPS request in C using OpenSSL.


How to make an https request in c with redirect following?

To make an HTTPS request in C with redirect following, you can use the popular library libcurl. Here is a simple example of how to perform an HTTPS request with redirect following using libcurl:

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#include <stdio.h>
#include <curl/curl.h>

size_t write_callback(char *ptr, size_t size, size_t nmemb, void *userdata) {
    // Write response data here
    printf("%s", ptr);
    return size * nmemb;
}

int main() {
    // Initialize libcurl
    curl_global_init(CURL_GLOBAL_ALL);
    CURL *curl = curl_easy_init();
    
    if(curl) {
        // Set the request URL
        curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
        
        // Set the callback function to handle the response data
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_callback);
        
        // Enable automatic following of HTTP redirects
        curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
        
        // Perform the request
        CURLcode res = curl_easy_perform(curl);
        
        if(res != CURLE_OK) {
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        }
        
        // Cleanup
        curl_easy_cleanup(curl);
    }
    
    // Cleanup libcurl
    curl_global_cleanup();
    
    return 0;
}


In this example, we initialize libcurl, set the request URL to "https://example.com", set a callback function to handle the response data, enable automatic following of redirects, and then perform the request. The response data will be printed to the console.


Note that you will need to have libcurl installed on your system and link against it when compiling your C code. You can do this by adding -lcurl to your compiler flags.


This is a basic example to get you started with libcurl. You can refer to the libcurl documentation for more advanced usage and customization options.

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