code: public void setProtectionBufferSize(int size)
          throws IOException, ServerException {
  
          if (size <= 0) {
              throw new IllegalArgumentException("size <= 0");
          }
  
          localServer.setProtectionBufferSize(size);
          try {
              Command cmd = new Command("PBSZ", Integer.toString(size));
              controlChannel.execute(cmd);
          } catch (FTPReplyParseException rpe) {
              throw ServerException.embedFTPReplyParseException(rpe);
          } catch (UnexpectedReplyCodeException urce) {
              throw ServerException.embedUnexpectedReplyCodeException(
                                  urce,
                                  "Server refused setting protection buffer size");
          }
          this.session.protectionBufferSize = size;
      }
docs: Sets protection buffer size (defined in RFC 2228)
  @param size the size of buffer