Search Exchange

Search All Sites

Nagios Live Webinars

Let our experts show you how Nagios can help your organization.

Contact Us

Phone: 1-888-NAGIOS-1


Remember Me


5 votes
Current Version
Last Release Date

Help Support Ethan Galstad's New Project:

Help Support Ethan

A Message From The Founder...

As the founder of Nagios, I'm asking for your help in a cause that's dear to my heart.

I'm launching a new project to help better the world by providing the information, ideas, and inspiration that I believe can improve the lives of people everywhere.

I know you're busy managing networks, but I would appreciate it if you would consider liking my Facebook page and showing your support for the content and messages I produce by sharing them with your friends and family.

You can learn more about my project by visiting Thank you for your time. I wish you all the best in your endeavors, whatever they may be.

- Ethan

This is Nagios plugin for Modbus TCP and Modbus RTU using RS232/RS485. It can be used to monitor PLCs and any other industrial devices supported Modbus TCP or Modbus RTU.
This is Nagios plugin for Modbus TCP and RTU.

Added many useful features:
- support of IPv6 / IPv4
- support of DNS names
- serial port connections (RS232 and RS485) with Modbus RTU (when compiled with libmodbus >= 3.0.0)
- support of many data formats (unsigned/signed int16_t, int32_t, float, double)
- support of several data orders (LSB, MSB and some others)
- retries can be sent to get reliable answer
- supports performance data
- supports creation dump of the registers in different formats (binary, hexadecimal, decimal)
- support binary dump as an input source for data (useful for off-line data)
- separate lock files for input and output

The lastest version can be found here
Reviews (4)
byfearstrider, October 28, 2018
I needed to make friends of ICP DAS (PET-7253) with Nagios3. Namely, to read discrete inputs. 1: OK, 0: Critical.
The plugin did a great job! Thanks!!
Need to add some more functionalities like MODBUS parsing
As of now plugin only capable to poll data ,but using this we can not parse data.Please modify this so we can easily monitor individual parameters using check commands..
Owner's reply

what do you mean by parse data?

Please create feature request as new issue on github:

byinvitu, September 19, 2015
a perfect plugin that can do calculation on values
bymarcof, October 8, 2012
1 of 1 people found this review helpful

I read in the description you could write a plugin for ModBus RTU / RS485. I need one :-) I've connected the RS485 directly to the nagios server by a comserver (serial over ethernet) modpoll is working so far... So the plugin should be able to just use a /dev/tty device.

Owner's reply

Hi, Marco. Thank you very much for the rating. Since version 0.4 check_modbus supports Modbus RTU over RS232/RS485 and some other features.