Jacob was an open source protocol framework written in Java. There are a few publications which explain, among other things, the ideas behind it. For example, have a look at the following.
Some of my publications are available at my publications page.
The old project home page may still be available at http://www.tml.hut.fi/Research/TeSSA/Old_pages/Jacob/jacob3.html
The jacob source code is available at sourceforge.