Hello,

We are comissioning a system with a S7-1200 [CPU 1214c-dc/dc/dc] Firmware v4.0.0 (TIA V13) , the Siemens PLC uses the block MB_SERVER to communication with a Modbus Client.

The Modbus Server Connection Id is = 10.

During the comissioning I noticed some weird status errors : 16#80C5 . I didn't know exacly the errors meaning, but I assume that they are internal status (like connect, disconnect, timeout, etc...) , but the communication works fine sometimes. this error will come only during disconnection from client.

After some time the communication stops working and the modbus client  error will be like "unable to write data from the transport connection. An existing was forcibly closed by the remort host".

Could you please help us ? Do you have some idea what can be wrong ?

I have also a RS-485 communication by using send PTP & RCV PTP & HMI in the X1 Interface, do you think they can affect the Modbus comms ?

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Split from Tips and sample program for MODBUS TCP.

Closed cause question posted twice.

The second thread with the subject Modbus client error is published within the conference Communication / Networks.

Best regards
Min_Moderator