The Modbus service supports a client/server communication for devices which are connected via Ethernet TCP/IP.

The client/server model is based on 4 message types:

• Request

• Indication

• Response

• Confirmation

Read data: The Modbus-TCP-Client (ibaPDA) establishes the connection to the Modbus server, sends periodically the request and waits for the response, which contains the requested data.

Write data: The Modbus-TCP-Client (ibaPDA) establishes the connection to the Modbus server, sends the request which contains the output data and waits for the response.

The port 502 is used for the Modbus TCP/IP communication by default, however you have got the possibility to enter other port numbers in ibaPDA.

With a ibaPDA-Interface-Modbus-TCP-Client license, ibaPDA can establish up to 64 connections, i.e., you can establish connections to up to 64 Modbus servers. The number can be extended to a max. of 256 by loading the license more than once.