Modbus Zabbix Proxy

[dade]

Hello everyone!

I have the following scenario:

Zabbix Server on a ubuntu vm, Zabbix Proxy on a Raspberry PI, and a sensor device connected to the Raspberry PI via USB (USB convert RS485).

I tested a python script on the Raspberry PI and I can collect the data correctly from the equipment via modbus, that is, the communication via modbus between the raspberry pi and the equipment is working.

My goal: I want the Zabbix Proxy configured on the Raspberry to do this collection via modbus.

I tried to create a host (monitored by Proxy) and configure the following item:
Zabbix Agent (Active)
keys:
Modbus.get [“/ dev / ttyUSB0 9600 N", 01.04.0001.0001] or
Modbus.get [“/ dev / ttyUSB0: 9600: 8N", 01.04.0001.0001]

But it did not work. I don't know if the problem is in the item, host or proxy. I didn't find much information about Modbus.get on the internet.

Thanks in Advanced!

[dade]

I got this error "Unknown metric Modbus.get" on item

[Hamardaban]

According to the documentation, you are incorrectly specifying the connection parameters, in particular the endpoint

https://www.zabbix.com/documentation/current/manual/appendix/items/modbus

First, specify the protocol - rtu or ascii

[dade]

Hello Hamardaban! Thanks for you reply!


Note1: On dmesg i have: [ 1036.808907] usb 1-1.3: FTDI USB Serial Device converter now attached to ttyUSB0

Note2: On python script i put: port='/dev/ttyUSB0' and it's working.

I tried diferents ways like:

Modbus.get["rtu://ttyUSB0",01,04,0001,0001]

Modbus.get["rtu://ttyS0:9600",01,04,0001,0001]

Modbus.get[rtu://ttyUSB0:9600:8n,01,04,0001,0001]

Modbus.get[ascii://ttyUSB0,01,04,0001,0001]

Modbus.get["rtu://dev/ttyUSB0:9600",01,04,0001,0001]

Modbus.get[rtu://dev/ttyUSB0,01,04,0001,0001]

Modbus.get["/dev/ttyUSB0 9600 N",01,04,0001,0001]

Modbus.get["/dev/ttyUSB0:9600:8n",01,04,0001,0001]

But it still didnt work.

[Hamardaban]

Specify which version of zabbix you use on the agent and proxy?

Does your device work as rtu or ascii?
Note that ascii only supports agent version 2.
Try using the agent's passive mode.

Modbus.get["rtu://dev/ttyUSB0:9600:8n",1....
+ verify all next parameter

[dade]

Ty again Hamardaban. I tried differents parameters but i got same error: Unknown metric Modbus.get

I gave up on using modbus.get and I decided to create an item to run the python script. I created the following item wih Zabbix Agent:

system.run [python home/pi/sht20_read_temp.py, wait]

But when I test it this error occurs:

Traceback (most recent call last):
File "home/pi/sht20_read_temp.py", line 6, in <module>
client.connect()
File "/usr/lib/python2.7/dist-packages/pymodbus/client/sync.py", line 476, in connect
self.socket.interCharTimeout = self.inter_char_timeout
AttributeError: 'NoneType' object has no attribute 'interCharTimeout'


Running the script directly in the raspberry shell works:

pi @ raspberrypi: ~ $ python sht20_read_temp.py
27.1

Other linux commands with system.run also works like "ls home/" pi or "cat home/pi/sht20_read_temp.py" ...

Can you help me with that too?

Thanks for you attention.

Phyton script below:


#!/usr/bin/env python
from pymodbus.client.sync import ModbusSerialClient as ModbusClient
import time

client = ModbusClient(method='rtu', port='/dev/ttyUSB0', timeout=1, stopbits = $
client.connect()

rr = client.read_input_registers(address=1, count=1, unit=1);
print rr.registers[0] / 10.0;

[Hamardaban]

Try to run the script on behalf of the user under which the zabbix server is running.

[dade]

Ty Hamardaban,

.. so How can i do this?

sorry about my noobises

[Hamardaban]

man sudo .

[dade]

So, i did in raspberry shell:

pi@raspberrypi:~ $ sudo -u pi python sht20_read_temp.py
26.9

it worked. But when i used zabbix user i got same item's error:

pi@raspberrypi:~ $ sudo -u zabbix python sht20_read_temp.py
Traceback (most recent call last):
File "sht20_read_temp.py", line 6, in <module>
client.connect()
File "/usr/lib/python2.7/dist-packages/pymodbus/client/sync.py", line 476, in connect
self.socket.interCharTimeout = self.inter_char_timeout
AttributeError: 'NoneType' object has no attribute 'interCharTimeout'


I created a item with: system.run[sudo -u pi python home/pi/sht20_read_temp.py,wait] .... and got this:


We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:

#1) Respect the privacy of others.
#2) Think before you type.
#3) With great power comes great responsibility.

sudo: no tty present and no askpass program specified

Ty Hamardaban i appreciate your tips.

[dade]

update, i tried again the modbus.get e now a got this:

2021/04/05 13:00:37.000729 check 'modbus.get["rtu://dev/ttyUSB0:9600:8n1",1,4,30001,1,int8,le,4]' is not supported: Unable to connect: permission denied

So it looks like I have to give zabbix some specific permission

[dade]

UPDATE: SOLVED

I did: sudo usermod -a -G dialout zabbix

So modbus.get worked!!! Thanks Hamardaban

although i would like to understand why i cant execute my python script through zabbix item.

[Spectator]

UPDATE: SOLVED

I did: sudo usermod -a -G dialout zabbix

So modbus.get worked!!! Thanks Hamardaban

although i would like to understand why i cant execute my python script through zabbix item.

Dear dade,
This post was a great help to me!
I would write this one line in CAPITAL LETTERS in the Zabbix Modbus documentation!
Thanks again!