def send_pdu(pdu)
      @transaction = 0 if @transaction.next > 65535
      @transaction += 1
      msg = @transaction.to_word + "\0\0" + (pdu.size + 1).to_word + @uid.chr + pdu
      @io.write msg

      log "Tx (#{msg.size} bytes): " + logging_bytes(msg)
    end
def send_pdu(pdu)
      @transaction = 0 if @transaction.next > 65535
      @transaction += 1
      msg = @transaction.to_word + "\0\0" + (pdu.size + 1).to_word + @uid.chr + pdu
      @io.write msg

      log "Tx (#{msg.size} bytes): " + logging_bytes(msg)
    end
overide method for RTU over TCP implamentaion
 @see Slave#query