I am trying to make a httpclient by libcurl

I have already used libcurl in C/C++ so I can help if you can tell me what you want to do exactly. The easy interface of curl is easy to use if all you want to do is performing a request on 1 thread and its ok to call a blocking function in curl that returns only when the request is done (or a specified timeout passes). To my best knowledge in http you can pass keys in standard way by:
1. specifying key value pairs in your url as your query string
2. If the "Content-Type: application/x-www-form-urlencoded" is specified in the header of your request then the server processes the uploaded content of your request basically as a query string

What has to be used in your case? If you don't know but you have a client that already works then install a Wireshark and capture the communication. Then right-click on one of the tcp packets involved in the communication and select the "Follow tcp stream" menupoint. If you are able to capture a file upload/delete I can tell you immediately what to do.