Currently, Parapin only supports a single parallel port at a time. It is not possible to have a single instance of the library manage multiple instances of a parallel port. This may be a problem for software that is simultaneously trying to control multiple parallel ports. Someday, I may fix this, but it will make the interface messier (a port handle will have to be passed to every function along with pin specifiers).
The C-library version of Parapin should probably do better probing of the parallel port, but any desire to do this was limited because it replicates what is already done by the Linux kernel and we expect that most production use of parapin will be with the kernel version anyway.
If you have bug reports, patches, suggestions, or any other comments, please feel free to visit the project page at http://parapin.sourceforge.net/. You may also contact the current maintainer, Al Hooton, directly at ahooton@users.sourceforge.net.