How to set Http header Fields using C programming - c

Question

I have code to save/read an http header, but in my application I want to set and send an http response header to my client. So how can I set an http header response for any request sent by the client?
Here is my code:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <curl/curl.h>
static size_t write_data(void *ptr, size_t size, size_t nmemb, void *stream)
{
int written = fwrite(ptr, size, nmemb, (FILE *)stream);
return written;
}
int main(void)
{
CURL *curl_handle;
static const char *headerfilename = "head.txt";
FILE *headerfile;
static const char *bodyfilename = "body.txt";
FILE *bodyfile;
curl_global_init(CURL_GLOBAL_ALL);
/* init the curl session */
curl_handle = curl_easy_init();
/* set URL to get */
curl_easy_setopt(curl_handle, CURLOPT_URL, "http://google.co.in");
/* no progress meter please */
curl_easy_setopt(curl_handle, CURLOPT_NOPROGRESS, 1L);
/* send all data to this function */
curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, write_data);
/* open the files */
headerfile = fopen(headerfilename,"wb");
if (headerfile == NULL) {
curl_easy_cleanup(curl_handle);
return -1;
}
bodyfile = fopen(bodyfilename,"wb");
if (bodyfile == NULL) {
curl_easy_cleanup(curl_handle);
return -1;
}
/* we want the headers be written to this file handle */
curl_easy_setopt(curl_handle, CURLOPT_WRITEHEADER, headerfile);
/* we want the body be written to this file handle instead of stdout */
curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, bodyfile);
/* get it! */
curl_easy_perform(curl_handle);
/* close the header file */
fclose(headerfile);
/* close the body file */
fclose(bodyfile);
/* cleanup curl stuff */
curl_easy_cleanup(curl_handle);
return 0;
}

Answer 1

As has been said in comments:
libcurl is a client-side library for doing the HTTP request. It will not help you implement the server response.
The server response will have to be sent by the server-side implementation and you haven't shown that or even explained how that is implemented. You cannot implement the server-side using libcurl.