libmodbus is a free software library to send/receive data with a device which respects the Modbus protocol. This library can use a serial port or an Ethernet connection.
The functions included in the library have been derived from the Modicon Modbus Protocol Reference Guide which can be obtained from Schneider at www.schneiderautomation.com.
The license of libmodbus is LGPL v2.1 or later.
The documentation is available as manual pages (man libmodbus to read general
description and list of available functions) or Web pages
www.libmodbus.org/documentation/. The
documentation is licensed under the Creative Commons Attribution-ShareAlike
License 3.0 (Unported) (http://creativecommons.org/licenses/by-sa/3.0/).
The official website is www.libmodbus.org.
The library is written in C and designed to run on Linux, Mac OS X, FreeBSD and QNX and Windows.
You will only need to install automake, autoconf, libtool and a C compiler (gcc or clang) to compile the library and asciidoc and xmlto to generate the documentation (optional).
To install, just run the usual dance, ./configure && make install. Run
./autogen.sh first to generate the configure script if required.
You can change installation directory with prefix option, eg. ./configure --prefix=/usr/local/. You have to check that the installation library path is
properly set up on your system (/etc/ld.so.conf.d) and library cache is up to
date (run ldconfig as root if required).
The library provides a libmodbus.pc file to use with pkg-config to ease your
program compilation and linking.
If you want to compile with Microsoft Visual Studio, you need to install http://code.google.com/p/msinttypes/ to fill the absence of stdint.h.
To compile under Windows, install MinGW and MSYS then select the common packages (gcc, automake, libtool, etc). The directory ./src/win32/ contains a Visual C project.
To compile under OS X with homebrew, you will need
to install the following dependencies first: brew install autoconf automake libtool.
The documentation can be generated in man pages and HTML files. The HTML files
aren't built by default by the make command but bymake htmldoc in
docs directory.
The documentation is also available online.
Some tests are provided in tests directory, you can freely edit the source code to fit your needs (it's Free Software :).
See tests/README for a description of each program.
For a quick test of libmodbus, you can run the following programs in two shells:
- ./unit-test-server
- ./unit-test-client
By default, all TCP unit tests will be executed (see --help for options).
It's also possible to run the unit tests with make check.
Before reporting a bug, take care to read the documentation (RTFM!) and to provide enough information:
- libmodbus version
- OS/environment/architecture
- libmodbus backend (TCP, RTU, IPv6)
- Modbus messages when running in debug mode (
man modbus_set_debug)
To report your problem, you can:
- fill a bug report on the issue tracker http://github.com/stephane/libmodbus/issues.
- or send an email to the libmodbus mailing list libmodbus@googlegroups.com.
If your prefer live talk when your're looking for help or to offer contribution, there is also a channel called #libmodbus on Freenode.