A demo version of the S7 Open Modbus TCP software for connecting a SIMATIC controller to systems of different manufacturers is available at the link below.
The downloadable demo version has no function or time restrictions. Modbus communication can also run without a valid license.
If the Modbus blocks are not licensed, the INTF LED or SF LED of the CPU flashes. In addition, messages are entered cyclically in the diagnostics buffer of the CPU and the status value A090 (hex) is output on the Modbus block in the user program.