C++

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

    static size_t WriteCallback(void *contents, size_t size, size_t nmemb, void *userp)
    {
        ((std::string*)userp)->append((char*)contents, size * nmemb);
        return size * nmemb;
    }
    int main(void)
    {

        CURL* curl;
        CURLcode res;
        std::string readBuffer;
        curl = curl_easy_init();
        if (curl) {

            curl_easy_setopt(curl, CURLOPT_URL, "https://httpbin.org/ip");
            curl_easy_setopt(curl, CURLOPT_PROXY, "http://tunnel.hahado.cn:31111");
            curl_easy_setopt(curl, CURLOPT_PROXYUSERPWD, "username:password");
            curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
            curl_easy_setopt(curl, CURLOPT_WRITEDATA, &readBuffer);
            /* Perform the request, res will get the return code */
            res = curl_easy_perform(curl);
                if(res != CURLE_OK){
                    fprintf(stderr, "curl_easy_perform() failed: %s\n",curl_easy_strerror(res));
            }

            /* always cleanup */
            curl_easy_cleanup(curl);

            std::cout << readBuffer << std::endl;
        }
        return 0;
    }