I'm using java io to retrieve text from a server that might output character such as é. then output it using System.err, they turn out to be '?'. I am using UTF8 encoding. what's wrong?

int len=0;

            char[]buffer=new char[1024];
            OutputStream os = sock.getOutputStream();
            InputStream is = sock.getInputStream();
            os.write(query.getBytes("UTF8"));//iso8859_1"));

            Reader reader = new InputStreamReader(is, Charset.forName("UTF-8"));


            do{
                len = reader.read(buffer);
             if (len>0) { 
                 if(outstring==null)outstring=new StringBuffer();
                 outstring.append(buffer,0,len);
             }
           }while(len>0);
            System.err.println(outstring);