POSTing a file to a web page and reading response

Hi.

I'm trying to read raw data from disk, POSTING it to a site that
converts the file to another format, and then read and save the
response.

I have only found on the web information on how to post a string, not
binary data.
My code only writes the html page to file, not the response file.

This is my code so far:
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    URL site = new URL("http://xxx.xxx.xxx.xxx");

            URLConnection conn = site.openConnection();
                       conn.setDoOutput(true);
                                conn.setRequestProperty
    ("Content-Type", "multipart/form-data");
            DataOutputStream dos;

            OutputStream os = conn.getOutputStream();
            dos = new DataOutputStream(os);
            FileInputStream fis = new FileInputStream("c:\\temp\
\test.xxx");

            int data;
            while ((data = fis.read()) != -1) {
                dos.write(data);

            }
            dos.flush();
            DataInputStream in = new
DataInputStream(conn.getInputStream());
            FileOutputStream fo = new FileOutputStream("c:\\temp\
\test.yyy");
            while ((data = in.read()) != -1) {
                fo.write(data);
            }
                        fo.flush();
            fo.close();
            dos.close();
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