code: public void retr(String arg) throws IOException {
          String msg;
          if (arg.equals("1"))
              msg = msg1;
          else
              msg = msg2;
          this.println("+OK " + msg.length() + " octets");
          this.writer.write(msg);
          this.println(".");
      }
docs: RETR command.
  
  @throws IOException
  unable to read/write to socket