Is a special protocol converter required to connect Modbus RTU serial interface devices to an Ethernet network? Is the serial device server sufficient?
Modbus TCP/IP to Modbus Serial Communication Module - ProSoft Technology, Inc.
tGW-700 Modbus TCP to RTU/ASCII Device Servers Table | ICP DAS USA Inc - Data Acquisition
MODBUS TCP on optic fiber with M340 - Schneider Electric Community