When LK210 is used as a Modbus TCP slave, you need to set the slave address in the program, as shown in the figure below, add the HS_ModbusTCP slave function block in the PLC, and set the address.
When the LK210 is a Modbus TCP slave, it supports up to 32 master links. When LK210 communicates with Modbus, port 502 is 502.