DoMore Modbus problem

[Gummi Ben]

Hello, my name is Gudmundur and I'm trying to read data from a KNX converter via Modbus TCP/IP.  I always get this error " Couldn't open TCP connection with specified device in MRX @0000005B (MRX at $Main@0)".  I tried to connect a Click CPU and was able to get data but not with the DoMore.  The main difference I see is that in the click I am allowed to enter the address "400001" my self but in the DoMore MRX instruction I'm only allowed to enter the offest. 
Attached is a screenshot of the DoMOre and the Click instruction.  What could be the problem ?

Regards, Gudmundur

[ADC Product Engineer]

Try leaving the Unit ID at 255.  Most devices do not need or want the slave address unless it is a gateway style of device.

[BobO]

The error indicates that the server isn't responding to the PLC and we were not able to establish the connection. Since your server address looks fine, it sounds like a network layer issue, which could be many different things. If you have confirmed that the PLC's IP/Netmask/Gateway addresses are compatible with the server's, try power cycling the switch between the two devices. As crazy as that sounds, we have seen cases where the route table in the switch is wrong and it simply won't talk. This generally occurs when the IP address of one of the devices has been changed.

If there are other devices connected to the Modbus server, it may have a limited number of concurrent connection, and may be rejecting the PLC's connection.

We have also seen devices that would only accept one server connection...the first...after which it needed to be power cycled before it would accept a new connection. Powercycling the server is the answer there.

Finally, when all else fails, we're happy to look at a Wireshark trace.

[Gummi Ben]

Solved, it was wrong MASK settings on the DoMore ethernet port.  Thank you all for this.

Regards, Guğmundur