Dear list. I'm the author of one of the Python bindings for JACK: https://jackclient-python.readthedocs.io/ I was a bit lazy when implementing a generator function that's supposed to yield all incoming MIDI events one-by-one. Here's the code if somebody is interested (it's using CFFI and the _lib object is a wrapper for the JACK API): def incoming_midi_events(self): event = self._event buf = _lib.jack_port_get_buffer( self._ptr, self._client.blocksize) for i in range(_lib.jack_midi_get_event_count(buf)): err = _lib.jack_midi_event_get(event, buf, i) # TODO: proper error handling if this ever happens: assert not err, err yield event.time, _ffi.buffer(event.buffer, event.size) As you can see, I didn't check the return value of jack_midi_event_get(), I just added an "assert" statement hoping that somebody would report it if the call to jack_midi_event_get() would ever fail. I didn't hear anything for a long time, but recently I got a bug report where the assertion was violated: https://github.com/spatialaudio/jackclient-python/issues/54 This shows that jack_midi_event_get() can raise an error, even if I check with jack_midi_get_event_count() beforehand. My question is now: how should I react to this error? Shall I ... * discard the current event and continue reading further events? * discard the current and all following events in this block? * raise an error? * do something else? Can I guarantee that no incoming MIDI events get lost? Another related question: what error code is supposed to be returned? The documentation (http://www.jackaudio.org/api/group__MIDIAPI.html#ga838c794bd1451bfd47edde1c…) mentions ENODATA, but according to my bug report, ENOBUFS (-105) was returned. Is this a bug in JACK or an omission in the documentation? I don't know which JACK version was used, the OS was Ubuntu 18.04 LTS 64 bits. cheers, Matthias