Specifications

ETH
ModbusTCP
M
ETH
ModbusTCP
S
ETH
ModbusTCP
S
ETH
ModbusTCP
S
ETH
ModbusTCP
S
Fig. 8.3: Modbus TCP
8.3. Modbus TCP, local TCP/IP connection
Note - Only works in Router mode.
TCP connection is established only locally between Modbus devices and the connected RipEX units.
TCP protocol overhead is not transmitted over the Radio channel. Secured TCP/IP transfer is not ne-
cessary because in Router mode every packet in the Radio channel is acknowledged on every radio
hop. A packet is therefore repeated directly in the part of the network where it is lost, not across the
entire radio network as in TCP/IP. This improves latency and increases network throughput.
ETH
ModbusTCP
LocalTCP
connection
M
ETH
ModbusTCP
LocalTCP connection
S
ETH
ModbusTCP
LocalTCP connection
S
ETH
ModbusTCP
LocalTCP connection
S
ETH
ModbusTCP
LocalTCP connection
S
Fig. 8.4: Modbus TCP local
Set your Modbus TCP Master to use a single IP to communicate with Modbus TCP Slaves (RipEX
ethernet IP) and set TCP port to 504. Communication begins on port 504 from where it is redirected
to other RipEX ports, corresponding to the individual RTU’s, based on negotiation with the Modbus
TCP Master.
To set up RipEX connected to Modbus TCP Master:
45© RACOM s.r.o. – RipEX Application notes
Modbus TCP/RTU