This is Nagios plugin for Modbus TCP and RTU. The first version of this plugin was taken from http://exchange.nagios.org/directory/Plugins/Network-and-Systems-Management/Check_modbus_tcp/details

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

In general, plugin can be build as usual

./autogen.sh ./configure make make install

When you are trying to build plugin under MinGW, then maybe you will need to define path for libmodbus explicitly.

libmodbus is installed by default in /usr/local/lib. In MinGW you will need to run

./configure LDFLAGS=-L/usr/local/lib CPPFLAGS=-I/usr/local/include

instead of just ./configure

For usage details see manual page or run ./check_modbus --help.