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Modbus TCP App Server not working

Modbus TCP App Server not working

Open
Occasional Contributor

Hi Community,

I am new in using Modbus TCP Server App.

I have setup a simple boolean variable in ctrlX PLC datalayer

Open_0-1725859438544.png

Modbus TCP Server:

Open_1-1725859520180.png

Modbus TCP Client: 

Open_2-1725859641980.png

However the value doesnt update the variable in plc is true in the client variable remain false, tried writing true doesnt work too. 

I tried using 2 ctrlX, 1 as modbus tcp client and another as modbus tcp server same issue.

Anyone had this issues? 

4 REPLIES 4

AndreasL
New Contributor

Does it make a difference if you change the PLC data type to a uint (the modbus registers are 16bit)? 

 

Open
Occasional Contributor

Hi @AndreasL ,

Reading works now after changing the variable to uint. Now i want to write the variable it doesnt work.

PLC:

Open_0-1725862704220.png

Modbus TCP Server:

Open_1-1725862810655.png

Modbus TCP Client:

Open_2-1725862865085.png

AndreasL
New Contributor

Can you write the variable from the datalayer? (So the symbol is readwrite)

Can you test with this master/client? 

https://github.com/ClassicDIY/ModbusTool

Open
Occasional Contributor

Hi @AndreasL 

Yes i am able to write the variable from the datalayer:

Open_0-1725865019274.png

Open_1-1725865045289.png

I tried using the ModbusTool reading worked but writing doesnt work.

Read:

Open_3-1725865163652.png

Write:

Open_4-1725865247810.png

Write succeeded but values in PLC did not change

Open_5-1725865287191.png

Open_6-1725865322116.png

ctrlX Apps:

Open_7-1725865370286.png

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