Thank you for the information. Just to update this thread: I had this old serial RS232 Ethernet converter: http://www.usconverters.com/index.php?main_page=product_info&cPath=66&products_id=225 laying around, I tried it out but it didn't work, I suppose its because this particular converter does not support Modbus over Ethernet. As far as I have read elsewhere RS232 Modbus over Ethernet is not the same as standard RS232 over Ethernet. I guess I will have to invest in a proper converter although the seem outrageously pricy.