Modbus TCP with VM-3P75CT

Q&A and troubleshooting
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1

Hello all.

I am trying to establish direct Modbus TCP communication between my computer and the VM-3P75CT.

What have I done so far:
Connect device to the local network.
Over Victron Connect, I can see the device IP.
Fom my computer, I am able to ping this device.

What is problem ?
When I am trying to send a request over Modbus TCP, I am getting Connection Refused message, no matter what.
So basically when I use on Linux command : telnet 502
Its end up with the message:
telnet: Unable to connect to remote host: Connection refused

Dont you have any idea, what may I be doing wrong ? Is this connection even possible ? Thanks

2

i use python to connect to the device with python and modbus tcp.
this works meanwhile quite well and i can query data.
see my example:

3

I have a HomeAssistant Modbus TCP file laying around somewhere if you are interested?

Because I have a Multiplus II connected I can query them from the Multiplus II which is the intended way. But you can also directly ask the vm-3p75ct directly if no Multiplus II is connected with this config.

4

Thanks for the proposal but i dont use Homeassistant, dont know if this is comparable. Actually i use now a Venus OS Raspberry from which i can query as well via ModbusTCP according to the CCGX register list which is a lot easier.
But sometimes due to wifi connection the venus device is not reachable so i fall back to ModbusUDP query directly and interestinlgy grid frequency seems only available via UDP directly.