First step is to just install the signal handler; see frysk.event.SignalEvent; and print that a cntrl-c occured. After that is pushing the event into things like the hpd and stepping engine so that they know that they should halt the current operation. (note that this doesn't mean trying to use Java 1.0's deprecated interrupt mechanism)
Ctrl-C handling for fhpd. frysk-core/frysk/hpd/ChangeLog: 2008-03-07 Teresa Thomas <tthomas@redhat.com> . * CLI.java (SteppingObserver.getMonitor): Add events to handle SIGINT. * ShellCommand.java (interpretCommand): Ditto. * SigIntHandler.java: New. frysk-core/frysk/bindir/ChangeLog: 2008-03-07 Teresa Thomas <tthomas@redhat.com> * fhpd.java (main): Add event to handle SIGINT.