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 www.modbus.org.
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 CMake (3.0 or higher) and a C compiler to compile the library and asciidoc and xmlto to generate the documentation (optional).
To install, the recommended way is to create a out-of-tree build-dir somewhere
out of the source tree and run cmake path/to/libmodbus/ && make. Or with ninja
cmake path/to/libmodbus -GNinja && make.
You can change installation directory by setting the CMAKE_INSTALL_PREFIX-
variable at CMake-configure time (inside the build-dir):
cmake -DCMAKE_INSTALL_PREFIX=/usr -GNinja path/to/libmodbus
ninja install
By default a shared-library is build, this can be toggled with the
BUILD_SHARED_LIBS-variable
cmake -DBUILD_SHARED_LIBS=OFF <...>
Building in with compiler-debug-options or release-options can be done by
specifying CMAKE_BUILD_TYPE:
cmake -DCMAKE_BUILD_TYPE=Release|Debug
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.
The library also provides a cmake/libmodbusConfig.cmake which, after
installation should allow you to include the libmodbus-library
(including its include-paths) in your CMake-based project.
If you want to compile with Microsoft Visual Studio, use cmake for Windows. It will generate a VCProject-file or NMake-files. You may need to install https://github.com/chemeris/msinttypes to fill the absence of stdint.h.
To compile under OS X with homebrew should work seemlessly as homebrew supports CMake.
The documentation is available online or as manual pages after installation.
The documentation is based on AsciiDoc.
To build the man-pages and/or the html-documentation you need to enable the CMake option
BUILD_DOCS and BUILD_DOCS_HTML, BUILD_DOCS_MAN respectively. If enabled the generated
man-pages will be installed.
If the necessary tools to build the documentation are not detected by cmake, these variables are forced to off.
cmake -DCMAKE_INSTALL_PREFIX=/usr -GNinja path/to/libmodbus -DBUILD_DOCS=ON
ninja doc
ninja install
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.
Tests are built by default, but this can be disable by setting the variable
BUILD_TESTING to OFF.
For a quick manual 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 ctest:
cmake -GNinja path/to/libmodbus
ninja
ctest
See CONTRIBUTING document.