Modbus TCP is a version of the Modbus protocol for Ethernet networks. The data model and function calls used by Modbus TCP and Modbus RTU are identical.
The encapsulation is different with the Modbus message “wrapped up” in a TCP/IP packet, and a checksum is not required ensure that the message arrives intact.
A master device initiates the communications, and a slave instrument only acts on the message if it has been sent to its own IP address.