Download with instructions link
Main features:
Midi channel messages real time monitoring (Note On/Off, AfterTouch, Pitch Bend, Control Change, Program Change) in readable format.
Midi common message and midi sync message real time monitoring.
Support for Active Sensing messages (http://www.blitter.com/~russtopia/MIDI/~jglatt/tech/midispec/sense.htm)
System Exclusive message real time monitoring.
Open source https://github.com/vanvught/rpidmx512/tree/master/rpi_midi_sniffer