Task: MAC vendor lookup
C: #include <curl/curl.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>

/* Length of http:
#define FIXED_LENGTH 16

struct MemoryStruct {
  char *memory;
  size_t size;
};
 
static size_t WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
  size_t realsize = size * nmemb;
  struct MemoryStruct *mem = (struct MemoryStruct *)userp;
 
  mem->memory = realloc(mem->memory, mem->size + realsize + 1);
 
  memcpy(&(mem->memory[mem->size]), contents, realsize);
  mem->size += realsize;
  mem->memory[mem->size] = 0;
 
  return realsize;
}

void checkResponse(char* str){
	char ref[] = "Vendor not found";
	int len = strlen(str),flag = 1,i;
	
	if(len<16)
		fputs(str,stdout);
	else{
		for(i=0;i<len && i<16;i++)
			flag = flag && (ref[i]==str[i]);
		
		flag==1?fputs("N/A",stdout):fputs(str,stdout);
	}
}

int main(int argC,char* argV[])
{
		if(argC!=2)
			printf("Usage : %s <MAC address>",argV[0]);
		else{
			CURL *curl;
			int len = strlen(argV[1]);
			char* str = (char*)malloc((FIXED_LENGTH + len)*sizeof(char));
			struct MemoryStruct chunk;
			CURLcode res;
 
			chunk.memory = malloc(1);
			chunk.size = 0;  
 
        if ((curl = curl_easy_init()) != NULL) {
				sprintf(str,"http:

                                curl_easy_setopt(curl, CURLOPT_URL, str);
				curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
				curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);
				
				free(str);
				
				res = curl_easy_perform(curl);
				
                if (res == CURLE_OK) {
				checkResponse(chunk.memory);
                                return EXIT_SUCCESS;
                }
				
                curl_easy_cleanup(curl);
			}
		}
        
        return EXIT_FAILURE;
}

C++: 


#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/connect.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <iostream>
#include <string>

bool get_mac_vendor(const std::string& mac, std::string& vendor) {
    namespace beast = boost::beast;
    namespace http = beast::http;
    namespace net = boost::asio;
    using tcp = net::ip::tcp;

    net::io_context ioc;
    tcp::resolver resolver(ioc);
    const char* host = "api.macvendors.com";

    beast::tcp_stream stream(ioc);
    stream.connect(resolver.resolve(host, "http"));

    http::request<http::string_body> req{http::verb::get, "/" + mac, 10};
    req.set(http::field::host, host);
    req.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);
    http::write(stream, req);

    beast::flat_buffer buffer;
    http::response<http::string_body> res;
    http::read(stream, buffer, res);

    bool success = res.result() == http::status::ok;
    if (success)
        vendor = res.body();

    beast::error_code ec;
    stream.socket().shutdown(tcp::socket::shutdown_both, ec);
    if (ec && ec != beast::errc::not_connected)
        throw beast::system_error{ec};

    return success;
}

int main(int argc, char** argv) {
    if (argc != 2 || strlen(argv[1]) == 0) {
        std::cerr << "usage: " << argv[0] << " MAC-address\n";
        return EXIT_FAILURE;
    }
    try {
        std::string vendor;
        if (get_mac_vendor(argv[1], vendor)) {
            std::cout << vendor << '\n';
            return EXIT_SUCCESS;
        } else {
            std::cout << "N/A\n";
        }
    } catch(std::exception const& e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }
    return EXIT_FAILURE;
}