How to upload file and json data with method POST use curlpp

I want to write C++ code with using curlpp library which work exactly as following example on curl if it possible of course.

> curl -H "Content-Type: application/json" -X POST -d '{"param1":"val1", "param2":"val2", "param3":"val3"}' --data-binary '@/tmp/somefolder/file.bin' https://my-api.somedomain.com:1024/my_command_url
>

I was able to write transfer json text with method POST but when I added upload command this library substitute PUT instead of POST.

I decided to post answer here, perhaps it will help somebody like me

static string post_request(const string url,const string body1,const string path2file)
{
   const string field_divider="&";
   stringstream result;
   try
   {
      using namespace std;

      // This block responsible for reading in the fastest way media file
      //      and prepare it for sending on API server
      ifstream is(path2file);
      is.seekg(0, ios_base::end);
      size_t size=is.tellg();
      is.seekg(0, ios_base::beg);
      vector<char> v(size/sizeof(char));
      is.read((char*) &v[0], size);
      is.close();
      string body2(v.begin(),v.end());

      // Initialization
      curlpp::Cleanup cleaner;
      curlpp::Easy request;
      list< string > headers;
      headers.push_back("Content-Type: application/json");
      headers.push_back("User-Agent: curl/7.77.7");

      using namespace curlpp::Options;

      request.setOpt(new Verbose(true));
      request.setOpt(new HttpHeader(headers));
      request.setOpt(new Url(url));
      request.setOpt(new PostFields(body1+field_divider+body2));
      request.setOpt(new PostFieldSize(body1.length()+field_divider.length()+body2.length()));
      request.setOpt(new curlpp::options::SslEngineDefault());
      request.setOpt(WriteStream(&result));
      request.perform();
   }
   catch ( curlpp::LogicError & e )
     {
       cout << e.what() << endl;
     }
   catch ( curlpp::RuntimeError & e )
     {
       cout << e.what() << endl;
     }

   return (result.str());

}