Playing some more with Modbus TCP on a NodeMCU0.9 using PlatformIO in VS-code and Universal Robots
Made a simple control of holdig register 10 (40011). By sending 101 or 202 it will light up leds on the ESP and sent a message via the terminal (baud 9600)
have fun - and remeber, only 1 client can be connected to a modbus server a time.
I also tested it with a Universal Robot CB3 sim (URSim), you can find my code in the folder (UR3CB3-SimpleESPModbusComm). You can downloaded it from UR Homepage (https://www.universal-robots.com/)
As always... Have fun with the data and code