Modbus-TCP is an open M2M protocol designed for communication among various devices. The communication takes place by exchanging data messages between a client and a server in a master-slave mode.

• Modbus-RTU
is a protocol that uses the RS-485 bus. It is frequently used in industrial applications, such as when connecting PLCs to displays, I/O interfaces and so on.
• Modbus-TCP
extends the previous Modbus-RTU protocol and is used in LAN (Ethernet) networks. The advantage of Modbus-TCP is its openness and compatibility with a wide range of industrial devices. Disadvantages of Modbus-TCP include a total lack of any security.

Modbus-TCP is frequently used in
• PLC (industrial controllers)
• SCADA systems (visualizations and basic control of industrial processes)