FR: Add the ability to distinguish between midi devices

[rhofour]

FR: Add the ability to distinguish between midi devices

[newlandsvalley]

What sort of applications do you want to build with this? When I started it, my only aim was to be able to play the MIDI keyboard that I'd just bought!

But I think you're right. If more than one input device connects, clients will need to discriminate between them and the obvious answer is to put the device id into each message. And for output we'd need both a multiplex send and a point-to-point(s) send. I suppose then we could build a MIDI router.

I don't think we'd need to bother too much about lost messages if a device disconnects. It's not as if we're re-inventing MQ with guaranteed once-only delivery semantics. We already listen to disconnections and so the sender will eventually be informed and can change his output options, with the proviso that in-transit messages will be lost.

[rhofour]

I've got two grid MIDI controllers (a Novation Launchpad Pro and a Midi Fighter) which have LEDs in them. I'm working on a program similar to Melodics (think DDR, but for MIDI controllers) where you can enter a pattern to practice, then get feedback on your timing as you do.

To make either of my controllers light up when you hit them you need to listen for their note on messages then send them back. The first problem I encountered was that my computer also has virtual MIDI Through ports that are connected to each other. So if I listen for a note on event then send it out I'll end up in a loop.

I'll probably start with adding IDs to input, then followup with another PR changing output.

[newlandsvalley]

@rhofour fixed via f0b3138