Modbus TCP is a variant of the Modbus protocol that embeds Modbus telegrams in TCP/IP packets and thus uses Ethernet-based networks. Functionally, Modbus-TCP is largely equivalent to Modbus-RTU, but it is transmitted via TCP/IP rather than over a serial connection.
Protocol and Transport Layer
With Modbus-TCP, protocol data is transmitted via the TCP/IP protocol, by default over TCP port 502. This allows existing network infrastructure—such as switches, routers, and firewalls—to be utilized, which simplifies integration into industrial Ethernet networks. The classic Modbus function codes are largely retained.
Use in Automation Networks
Modbus-TCP is primarily used in Ethernet-based automation and control systems, for example, to connect controllers, I/O modules, measuring devices, and control systems. Many modern measurement and data acquisition systems support Modbus-TCP as a server and/or client to make measured values available over standard networks or to read data from existing Modbus-TCP structures. Delphin measurement and data acquisition systems can also typically be integrated into existing Ethernet and control system environments via Modbus-TCP.