After I have started the Slave Demon it takes about 30 - 50 seconds for the first values (send via TCP/IP) to arrive. I have a Graph that plots all the18 read values for me and it always takes a long time to see them jump fom 0 to another value. Afterwards there remains a delay of about 30 seconds regarding how current the shown values are.
I can't post the VI here because it uses a lot of SubVIs which would make it not runable anyway. However, I already checked the Modbus Salve Example VI and there I have the same delay as in my own programm.
Problem solved. It was the device (a data logger) that was acting so slow in sending the data while it was acting as the master. I changed it now to be the slave and read its holding registers. This way the values arrive "immediatelly".