func (cli *DockerCli) streamHelper(method, path string, setRawTerminal bool, in io.Reader, stdout, stderr io.Writer, headers map[string][]string) error {
	if (method == "POST" || method == "PUT") && in == nil {
		in = bytes.NewReader([]byte{})
	}

	req, err := http.NewRequest(method, fmt.Sprintf("/v%s%s", api.APIVERSION, path), in)
	if err != nil {
		return err
	}
	req.Header.Set("User-Agent", "Docker-Client/"+dockerversion.VERSION)
	req.URL.Host = cli.addr
	req.URL.Scheme = cli.scheme
	if method == "POST" {
		req.Header.Set("Content-Type", "plain/text")
	}

	if headers != nil {
		for k, v := range headers {
			req.Header[k] = v
		}
	}
	resp, err := cli.HTTPClient().Do(req)
	if err != nil {
		if strings.Contains(err.Error(), "connection refused") {
			return fmt.Errorf("Cannot connect to the Docker daemon. Is 'docker -d' running on this host?")
		}
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 400 {
		body, err := ioutil.ReadAll(resp.Body)
		if err != nil {
			return err
		}
		if len(body) == 0 {
			return fmt.Errorf("Error :%s", http.StatusText(resp.StatusCode))
		}
		return fmt.Errorf("Error: %s", bytes.TrimSpace(body))
	}

	if api.MatchesContentType(resp.Header.Get("Content-Type"), "application/json") {
		return utils.DisplayJSONMessagesStream(resp.Body, stdout, cli.outFd, cli.isTerminalOut)
	}
	if stdout != nil || stderr != nil {
		// When TTY is ON, use regular copy
		if setRawTerminal {
			_, err = io.Copy(stdout, resp.Body)
		} else {
			_, err = stdcopy.StdCopy(stdout, stderr, resp.Body)
		}
		log.Debugf("[stream] End of stdout")
		return err
	}
	return nil
}
// Check to make sure request's Content-Type is application/json
func checkForJson(r *http.Request) error {
	ct := r.Header.Get("Content-Type")

	// No Content-Type header is ok as long as there's no Body
	if ct == "" {
		if r.Body == nil || r.ContentLength == 0 {
			return nil
		}
	}

	// Otherwise it better be json
	if api.MatchesContentType(ct, "application/json") {
		return nil
	}
	return fmt.Errorf("Content-Type specified (%s) must be 'application/json'", ct)
}