Question

我正在尝试通过C ++的curl库做一些请求。我可以成功执行我的请求并通过命令行获得正确的响应，但我无法通过 C ++代码获得正确的响应。我的命令行命令看起来像这样

curl -X POST -H 'Accept: application/json' -H 'Content-Type: application/json' -H 'Authorization: <some_hash_value>' -k <my_full_url> -data '<my_json_string>'

工作正常。现在我尝试用C ++代码做同样的请求。我的代码看起来像这样

void performRequest(const std::string& json, const void* userData, CallbackFunction callback)
{
    struct curl_slist* headers = NULL;

    headers = curl_slist_append(headers, "Accept: application/json");
    headers = curl_slist_append(headers, "Content-Type: application/json");
    headers = curl_slist_append(headers, (std::string("Authorization: ") + m_authorization).c_str());

    CURL* curlHandle = curl_easy_init();
    if (!curlHandle)
    {
        std::cerr << "Curl handler initialization failed";
    }

    curl_easy_setopt(curlHandle, CURLOPT_NOSIGNAL, 1);
    curl_easy_setopt(curlHandle, CURLOPT_HTTPHEADER, headers);

    // specify target URL, and note that this URL should include a file name, not only a directory
     curl_easy_setopt(curlHandle, CURLOPT_URL, m_url.c_str());

    // enable uploading
    curl_easy_setopt(curlHandle, CURLOPT_UPLOAD, 1L);

    // set HTTP method to POST
    curl_easy_setopt(curlHandle, CURLOPT_CUSTOMREQUEST, "POST");

    // set json data; I use EXACTLY the same string as in command line
    curl_easy_setopt(curlHandle, CURLOPT_COPYPOSTFIELDS, json.c_str());

    // set data size
    curl_easy_setopt(curlHandle, CURLOPT_POSTFIELDSIZE_LARGE, json.size());

    // set user data for getting it in response
    curl_easy_setopt(curlHandle, CURLOPT_WRITEDATA, userData);    // pointer to a custom struct

    // set callback function for getting response
    curl_easy_setopt(curlHandle, CURLOPT_WRITEFUNCTION, callback);    // some callback

    // send request
    curl_easy_perform(curlHandle);

    curl_easy_cleanup(curlHandle);
    curl_slist_free_all(headers);
}

但是，出于某种原因，我从服务器的响应中得到一个错误，我可以假设我的代码的请求不等于命令行的命令。似乎身体没有发送。当我使用CURLOPT_DEBUGFUNCTION转储调试信息时，我无法看到我的请求Json正文。

这是什么问题？我究竟做错了什么？有什么想法吗？

Answer 1

以下是适合您的示例代码。

请注意我：

已移除CURLOPT_UPLOAD，因为它实际上并不是您实际上传的内容，而只是做了一个简单的POST。
将CURLOPT_CUSTOMREQUEST更改为CURLOPT_POST（并非它应该重要），但我发现它更清晰。
重新排序CURLOPT_POSTFIELDSIZE_LARGE和CURLOPT_COPYPOSTFIELDS
为了此示例代码，删除了CURLOPT_WRITEDATA行。

我仅通过连接到nc -l localhost 80

的实例来测试以下内容

 static size_t callback(char *ptr, size_t size, size_t nmemb, void *userdata)
 {
   string s(ptr);
   cout << s << endl;
   return size * nmemb;
 }


 int main(int argc, char** argv)
 {
   string m_authorization("PWNED");
   string m_url("http://localhost");
   string m_json("{}");

   curl_global_init(CURL_GLOBAL_ALL);

   CURL* curlHandle = curl_easy_init();

   struct curl_slist* headers = nullptr;
   headers = curl_slist_append(headers, "Accept: application/json");
   headers = curl_slist_append(headers, "Content-Type: application/json");
   headers = curl_slist_append(headers, (std::string("Authorization: ") + m_authorization).c_str());

   curl_easy_setopt(curlHandle, CURLOPT_NOSIGNAL, 1);
   curl_easy_setopt(curlHandle, CURLOPT_HTTPHEADER, headers);

   // specify target URL, and note that this URL should include a file name, not only a directory
   curl_easy_setopt(curlHandle, CURLOPT_URL, m_url.c_str());

   // <= You are not uploading anything actually, this is a simple POST with payload
   // enable uploading
   // curl_easy_setopt(curlHandle, CURLOPT_UPLOAD, 1L);

   // set HTTP method to POST
   curl_easy_setopt(curlHandle, CURLOPT_POST, 1L);

   // set data size before copy
   curl_easy_setopt(curlHandle, CURLOPT_POSTFIELDSIZE_LARGE, m_json.size());

   // set json data; I use EXACTLY the same string as in command line
   curl_easy_setopt(curlHandle, CURLOPT_COPYPOSTFIELDS, m_json.c_str());

   // set user data for getting it in response
   // curl_easy_setopt(curlHandle, CURLOPT_WRITEDATA, userData);    // pointer to a custom struct

   // set callback function for getting response
   curl_easy_setopt(curlHandle, CURLOPT_WRITEFUNCTION, callback);    // some callback

   // send request
   curl_easy_perform(curlHandle);

   curl_slist_free_all(headers);

   curl_easy_cleanup(curlHandle);
   curl_global_cleanup();
   return 0;
 }

Answer 2

问题已解决坦克Rocki和drew010的评论。

我已删除CURLOPT_CUSTOMREQUEST，CURLOPT_UPLOAD和CURLOPT_NOSIGNAL设置语句，因为不需要它们。
我还删除了设置CURLOPT_POSTFIELDSIZE_LARGE的行，但如果在设置CURLOPT_COPYPOSTFIELDS之前设置它就可以正常工作。如果未在CURLOPT_COPYPOSTFIELDS之前设置大小，则假定数据为零终止字符串;否则，存储的大小会通知库有关要复制的字节数。在任何情况下，CURLOPT_COPYPOSTFIELDS后都不得更改尺寸，除非另行发出CURLOPT_POSTFIELDS或CURLOPT_COPYPOSTFIELDS选项。（见：curl.haxx.se/libcurl/c/CURLOPT_COPYPOSTFIELDS.html）

Answer 3

在windows中，你必须使用以下函数初始化winsock东西

curl_global_init(CURL_GLOBAL_ALL);

Curl命令行有效，C ++ curl库没有

3 个答案: