Error 404 when trying to get refresh token using CURL C++

Hi pakk4,

Before trying to do something read carefully all relevant documents (i.e at least curllib and Dropbox API documentation), something you skipped as seems. 🙋

In addition to what Greg said, be careful not to pass unsupported types (don't rely on C++ type checking since libcurl is NOT C++, but a clear C library, so wont receive error or warning). By default (i.e. not explicitly changed) data type is supposed to be a pointer to FILE, not something else!

Some pseudocode follows:

const char* constexpr oauth2_token = "https://api.dropboxapi.com/oauth2/token";

void somefunc() {
  auto callback = [](char *ptr, size_t size, size_t nmemb, void *userdata) -> size_t {
    std::string& dataBuf = *(std::string*)userdata;
    dataBuf.append(ptr, size*nmemb);
    return size*nmemb;
  };
  CURL *curl = curl_easy_init();
  if (curl) {
    std::string dataBuf;
    std::string body("grant_type=authorization_code&code=");
    body += "<your access code>";
    curl_easy_setopt(curl, CURLOPT_URL, oauth2_token);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, body.c_str());
    curl_easy_setopt(curl, CURLOPT_USERPWD, "<APP_KEY>:<APP_SECRET>");
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, callback);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)&dataBuf);
    CURLcode res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
    
    // ... do whatever you want with your result here.
  }
}

Adapt it to your needs.

Good luck.