by Frank Rysanek
of FCC Prumyslove Systemy s.r.o.
[ rysanek AT fccps DOT cz ]
Once upon a time, years ago, I've written a Modbus library for Linux. It was decided not to give it away as a free download on our website. If you're interested, send me an e-mail.
There is a manual to the library, and the header file is also well commented. The source tarball contains small example applications - including a trivial analyzer of Modbus/RTU. See the authors readme for some credits and history.
Based on that library, I've also written a simple relay demon. Again not available as a free download... To give you an idea of its capabilities, here are two example config files (and a manual in Czech).