Uploading some binary file to http server

UploadResource.java

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.nio.file.Files;

public class UploadResource {

    // Uploading some binary file to http server

    public static void main(String[] args) {
        uploadFile(new File("some/path/to/file.txt"));
    }

    static void uploadFile(File file) {

        if ( !file.exists()) return;

        String serverUrl = "http://127.0.0.1";
        String charset = "UTF-8";
        String boundary = Long.toHexString(System.currentTimeMillis());
        String CRLF = "\r\n";

        try {

            // Establishing connection with server
            URLConnection connection = new URL(serverUrl).openConnection();
            connection.setDoOutput(true);
            connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);

            try (
                // Opening output stream with server
                OutputStream outputStream = connection.getOutputStream();
                PrintWriter printWriter = new PrintWriter(new OutputStreamWriter(outputStream, charset), true) )
            {

                // Writing header data to server
                printWriter.append("--")
                        .append(boundary)
                        .append(CRLF);

                printWriter.append("Content-Disposition: form-data; name=\"fileIndexName\"; filename=\"")
                        .append(file.getName())
                        .append("\"")
                        .append(CRLF);

                printWriter.append("Content-Type: ")
                        .append(URLConnection.guessContentTypeFromName(file.getName()))
                        .append(CRLF);

                printWriter.append("Content-Transfer-Encoding: binary")
                        .append(CRLF);

                printWriter.append(CRLF).flush();

                // Writing binary data to server output stream
                Files.copy(file.toPath(), outputStream);

                outputStream.flush();

                printWriter.append(CRLF).flush();

                printWriter.append("--")
                        .append(boundary)
                        .append("--")
                        .append(CRLF)
                        .flush();

                // Server http response code
                int responseCode = ((HttpURLConnection) connection).getResponseCode();

                // Buffering response body
                BufferedReader bufferedReader = new BufferedReader(
                        new InputStreamReader((connection.getInputStream())));
                StringBuilder responseBody = new StringBuilder();
                String responseBodyLine;
                while ((responseBodyLine = bufferedReader.readLine()) != null) {
                    responseBody.append(responseBodyLine);
                }

                System.out.println("Server returned http status "
                        + responseCode
                        + " from url "
                        + serverUrl
                        + " with response body "
                        + responseBody.toString());

            }

        } catch (Exception ex) {
            // Http Status >= 500 got here
            ex.printStackTrace();
        }
    }
}