Copyright © 2015-2026 Pascal JEAN, All rights reserved.
mbpoll is a command line utility to communicate with ModBus slave (RTU or TCP).
This is a multiplatform project, the compilation was tested on GNU Linux
x86, x86_64, armhf and arm64 (Armbian/Raspbian), Microsoft Windows, and macOS.
Development of major version 1 of mbpoll is complete, version 2 using libmodbuspp is under development. Proposals for new features will be transferred to this new branch.
mbpoll can:
- read discrete inputs
- read and write binary outputs (coil)
- read input registers
- read and write output registers (holding register)
The reading and writing registers may be in decimal, hexadecimal or floating single precision.
Note: mbpoll's output syntax and command line option syntax is similar to the original modpoll command line program published by proconX. However mbpoll is a completely independent project and based on different source code than the original modpoll program. mbpoll is distributed under the GPL license, but the original modpoll program is not covered by the GPL license.
The fastest and safest way to install mbpoll is to use the APT repository from piduino.org, so you should do the following :
wget -O- http://www.piduino.org/piduino-key.asc | sudo gpg --dearmor --yes --output /usr/share/keyrings/piduino-archive-keyring.gpg
echo "deb [signed-by=/usr/share/keyrings/piduino-archive-keyring.gpg] http://apt.piduino.org $(lsb_release -c -s) piduino" | sudo tee /etc/apt/sources.list.d/piduino.list
sudo apt update
sudo apt install mbpoll
This repository provides mbpoll and libmodbus (version 3.1.7) packages for
i386, amd64, armhf and arm64 architectures.
Using Homebrew to install mbpoll and its dependencies using:
brew install mbpoll
For example, for a debian system:
-
Install libmodbus (Version >= 3.1.7) :
$ sudo apt-get install build-essential libtool git-core autoconf automake $ git clone https://github.com/stephane/libmodbus.git $ cd libmodbus $ ./autogen.sh $ ./configure $ make $ sudo make install
You can also install it with apt if the version of libmodbus is greater than or equal to 3.1.7.
For example to query a debian system:
$ apt-cache show libmodbus-dev
-
Install piduino only if you want to manage the RS485 with a GPIO signal:
$ sudo apt-get install cmake libcppdb-dev pkg-config libsqlite3-dev sqlite3 libudev-dev $ git clone https://github.com/epsilonrt/piduino.git $ cd piduino $ git checkout dev $ mkdir build $ cd build $ cmake .. $ make $ sudo make install -
Generate Makefile with cmake:
$ sudo apt-get install cmake pkg-config $ cd mbpoll $ mkdir build $ cd build $ cmake .. -
Compile and install mbpoll:
$ make $ sudo make install $ sudo ldconfig
If you prefer, you can in the place of direct compilation create a package and install it:
$ make package
$ sudo dpkg -i *.deb
In some cases, when installing pkg-config for the first time, it may be necessary to set the PKG_CONFIG_PATH environment variable before running cmake, so that pkg_check_modules can find libmodbus in /usr/local/lib/. This can be done with the following command: export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:$PKG_CONFIG_PATH. Make sure to adjust the path if your pkgconfig directory is located elsewhere.
That's all !
For Windows, you can follow the instructions in the README-WINDOWS.md file.
The following command is used to read the input registers 1 and 2 of the slave at address 33 connected through RTU /dev/ttyUSB2 (38400 Bd)
$ mbpoll -a 33 -b 38400 -t 3 -r 1 -c 2 /dev/ttyUSB2
mbpoll 1.5 - Modbus® Master Simulator
Copyright (c) 2015-2023 Pascal JEAN, https://github.com/epsilonrt/mbpoll
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions; type 'mbpoll -w' for details.
Protocol configuration: Modbus RTU
Slave configuration...: address = [33]
start reference = 1, count = 2
Communication.........: /dev/ttyUSB2, 38400-8E1
t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, input register table
-- Polling slave 33... Ctrl-C to stop)
[1]: 9997
[2]: 10034
-- Polling slave 33... Ctrl-C to stop)
[1]: 10007
[2]: 10034
-- Polling slave 33... Ctrl-C to stop)
[1]: 10007
[2]: 10034
-- Polling slave 33... Ctrl-C to stop)
[1]: 10007
[2]: 10034
^C--- /dev/ttyUSB2 poll statistics ---
4 frames transmitted, 4 received, 0 errors, 0.0% frame loss
everything was closed.
Have a nice day !
A complete help is available with the -h option.
On Unix systems, a man page is also available: man mbpoll
usage : mbpoll [ options ] device|host [ writevalues... ] [ options ]
ModBus Master Simulator. It allows to read and write in ModBus slave registers
connected by serial (RTU only) or TCP.
Arguments :
device Serial port when using ModBus RTU protocol
COM1, COM2 ... on Windows
/dev/ttyS0, /dev/ttyS1 ... on Linux
/dev/ser1, /dev/ser2 ... on QNX
host Host name or dotted IP address when using ModBus/TCP protocol
writevalues List of values to be written.
If none specified (default) mbpoll reads data.
If negative numbers are provided, it will precede the list of
data to be written by two dashes ('--'). for example :
mbpoll -t4:int /dev/ttyUSB0 -- 123 -1568 8974 -12
General options :
-m # mode (rtu or tcp, TCP is default)
-a # Slave address (1-255 for rtu, 0-255 for tcp, 1 is default)
for reading, it is possible to give an address list
separated by commas or colons, for example :
-a 32,33,34,36:40 read [32,33,34,36,37,38,39,40]
-r # Start reference (1 is default)
for reading, it is possible to give an address list
separated by commas or colons
-c # Number of values to read (1-125, 1 is default)
-u Read the description of the type, the current status, and other
information specific to a remote device (RTU only)
-t 0 Discrete output (coil) data type (binary 0 or 1)
-t 1 Discrete input data type (binary 0 or 1)
-t 3 16-bit input register data type
-t 3:int16 16-bit input register data type with signed int display
-t 3:hex 16-bit input register data type with hex display
-t 3:string 16-bit input register data type with string (char) display
-t 3:int 32-bit integer data type in input register table
-t 3:float 32-bit float data type in input register table
-t 4 16-bit output (holding) register data type (default)
-t 4:int16 16-bit output (holding) register data type with signed int display
-t 4:hex 16-bit output (holding) register data type with hex display
-t 4:string 16-bit output (holding) register data type with string (char) display
-t 4:int 32-bit integer data type in output (holding) register table
-t 4:float 32-bit float data type in output (holding) register table
-0 First reference is 0 (PDU addressing) instead 1
-B Big endian word order for 32-bit integer and float
-1 Poll only once only, otherwise every poll rate interval
-l # Poll rate in ms, ( > 100, 1000 is default)
-o # Time-out in seconds (0.01 - 10.00, 1.00 s is default)
-q Quiet mode. Minimum output only
-x Print address (reference) in hexadecimal format
-Q Enable MAX_SLAVE quirk (accept slave id 0-255)
-X Enable REPLY_TO_BROADCAST quirk (send reply to broadcast)
Options for ModBus / TCP :
-p # TCP port number (502 is default)
Options for ModBus RTU :
-b # Baudrate (1200-921600, 19200 is default)
-d # Databits (7 or 8, 8 for RTU)
-s # Stopbits (1 or 2, 1 is default)
-P # Parity (none, even, odd, even is default)
-R [#] RS-485 mode (/RTS on (0) after sending)
Optional parameter for the GPIO RTS pin number
-F [#] RS-485 mode (/RTS on (0) when sending)
Optional parameter for the GPIO RTS pin number
-h Print this help summary page
-V Print version and exit
-v Verbose mode. Causes mbpoll to print debugging messages about
its progress. This is helpful in debugging connection...
Pull requests are welcome! Please read CONTRIBUTING.md before submitting.
All contributions must target the dev branch — master is reserved for stable releases only.
mbpoll is free software licensed under the GNU General Public License v3.0.