FancyModbus Library & Tools


fancmodbus is a wrapper library for the libmodbus library, which can be found under

The modbus protocol is an industry standard protocol for controlling switchboards over serial lines or TCP. The standard is maintained at

Location of Packages

SVN: svn+ssh://




These packages are standalone programs to deal with the modbus protocol:


Installing the fancymodbus tools and simulator
apt-get install fancymodbus-tool fancymodbus-simulator

Library only

If you only need the library, install the following packages:

Install fancymodbus shared library components
apt-get install libfancymodbus1 libfancymodbus

Debug symbols

All packages have a counterpart containing debug symbols for gdb:

Install fancymodbus debug symbols
fancymodbus-tool-dbg fancymodbus-simulator-dbg libfancymodbus-dbg

Using the command line tool

Read Output Bits

The fancymodbus-tool client lets you read and write DO output bits/coils using the following commands:

fancymodbus-client writeDO 1 0x105 1 0 1 0 1
fancymodbus-client readDO 1 0x105 5

These example reads and writes 5 output bits starting with address 0x105.

If you do not want to conenct to the locally listening fancymodbus-simulator, you need to specify the IP of a real device like

Configuring fancymodbus-simulator

Edit /etc/fancymodbus/simulator.conf and change the listen port or the number of registers.

For the most part you should not need to edit the default configuration, which listens to and provides for 512 registers of each kind.

Activate the daemon in /etc/default/fancymodbus-simulator

Activate fancymodbus-simulator in /etc/default/fancymodbus-simulator
# set to yes if you want automatic starting

Start the daemon

Starting the fancymodbus-simulator daemon
/etc/init.d/fancymodbus-simulator start

The daemon logs it's diagnostics to /var/log/syslog