The robot controller supports Modbus over Ethernet (Modbus TCP). The Modbus interface is a widely used communication protocol in the automation industry today, often used when PLCs need to communicate with peripherals like sensors, actuators and instrumentation.
The robot comes with capabilities for a Modbus Server (Slave) as well as a Modbus Client (Master). By definition Modbus RTU uses the terms Master-Slave, in Modbus TCP/IP however, these terms translate to the Client–Server model. A Modbus Server is called a Slave and a Modbus Client is called a Master.
The Server is always running on the robot and your equipment can access the Server at any time to read and write values. This is mainly used when a PLC is present within your application. The Modbus Client functionality, however, is mainly used when no PLC is present, and you want to access a Modbus Device such as a Modbus IO Block to expand the IO capabilities of the robot.