libcurl

链接地址：https://curl.se/libcurl/

优点：普遍使用
示例代码：

#include <curl/curl.h>
#include <iostream.h>
#include <string>
#include <stdint.h>

struct memory
{
    char *response;
    size_t size;
    memory()
    {
        response = NULL;
        size = 0;
    }
    ~memory()
    {
        if (response)
        {
            delete[] response;
            response = NULL;
            size = 0;
        }
    }
};

static size_t cb(void *data, size_t size, size_t nmemb, void *userp)
{
    size_t realsize = size * nmemb;
    struct memory *mem = (struct memory *)userp;

    char *ptr = (char*)realloc(mem->response, mem->size + realsize + 1);
    if(ptr == NULL)
        return 0;  /* out of memory! */

    mem->response = ptr;
    memcpy(&(mem->response[mem->size]), data, realsize);
    mem->size += realsize;
    mem->response[mem->size] = 0;

    return realsize;
}

int main()
{
	CURL *curl = curl_easy_init();
    if (!curl)
    {
        std::clog << "curl_easy_init call failed!" << std::endl;
        return -1;
    }
	// set url
    curl_easy_setopt(curl, CURLOPT_URL, "http://google.com/");
    // set callback function
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, cb);
    // 	set timeout
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 10);
    // set compress opt [notice: Better set it, otherwise it's download slow]
    curl_easy_setopt(curl, CURLOPT_ACCEPT_ENCODING, "gzip"); // [br, gzip, deflate]
    struct memory chunk;
    /* we pass our 'chunk' struct to the callback function */
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);
    CURLcode res = curl_easy_perform(curl);
    if (CURLE_OK != res)
    {
        std::clog << "error:" << curl_easy_strerror(res) << std::endl;
        return -1;   
    }
    std::clog << chunk.response << std::endl;
    curl_easy_cleanup(curl);
	return 0;
}

cpp-httplib

链接地址：https://github.com/yhirose/cpp-httplib.git

优点：header-only && cross platform
示例代码：

#include "cpp-httplib/httplib.h"
int main()
{
	httplib::Client cli("es-cn-xxxx.elasticsearch.aliyuncs.com", 9200);
    cli.set_basic_auth("xxx", "xxx");
    httplib::Headers headers = {
        {"Accept-Encoding", "gzip"}
    }; // [notice: Better set it, otherwise it's download slow]
    auto res = cli.Post("url", headers, "post", "application/json");
}