Control which ports are opened

[briansorahan]

Idea spawned from this discussion #1
This would allow users to have more control over which ports they use.

[kisielk]

I don't think opening all the ports is necessarily a good idea, it uses up unnecessary resources and I think some systems like Windows only allow a port to be opened once. However exposing all the ports to the user of the package and allowing them to choose which one to open would be good.

[briansorahan]

I looked at how to do this with alsa rawmidi (which I prefer over the more complicated sequencer interface).
It looks like all you can do is open a given device and either open just an input, just an output, or both http://www.alsa-project.org/alsa-doc/alsa-lib/group___raw_midi.html#ga2ab783051deeb7eb37eb568b76448889
I don't think CoreMIDI is limited in this way, but if this package supports both then alsa rawmidi might be the limiting factor.
My understanding of alsa rawmidi could also be incomplete

[briansorahan]

@kisielk How about flags to control which ports are opened? I'm open to suggestion on what this issue should be about.

Based on what I know about alsa we might be limited to

FlagOpenInput
FlagOpenOutput

I'm not sure how to with a device that had multiple ins/outs using alsa rawmidi