jamod is an object oriented implementation of the Modbus protocol, realized 100% in Java. It allows to quickly realize master and slave applications in various transport flavors (IP and serial).
unfortunately, jamod has many bugs and it's still not a useful project. there are free projects that seems to me much better, for instance either jlibmodbus or j2mod.
After years of waiting for Deiter to add more messages, I've forked a new project on SourceForge -- j2mod. I can't keep waiting for "jamod" to become a useful product. Sorry. I've started posting JARs and should have a complete Modbus implementation in a few weeks. The only untested message in j2mod is WRITE FILE RECORD, which jamod doesn't even have.