code: public byte[] sendUnbindResp(OutputStream os, int commandStatus,
              int sequenceNumber) throws IOException {
          byte[] b = pduComposer.unbindResp(commandStatus, sequenceNumber);
          writeAndFlush(os, b);
          return b;
      }
docs: /*
  (non-Javadoc)
  
  @see org.jsmpp.PDUSender#sendUnbindResp(java.io.OutputStream, int, int)