Why doesn't this simple CoreMIDI program produce MIDI output?

Question

Here is an extremely simple CoreMIDI OS X application that sends MIDI data. The problem is that it doesn\'t work. It compiles fine, and runs. It reports no errors, and does

Answer 1

A little detail that others are skipping: the time parameter of MIDIPacketListAdd is important for some musical apps.

Here is an example of how you can retrieve it:

#import 
MIDITimeStamp midiTime = mach_absolute_time();

Source: Apple Documentation

And then, applied to the other examples here:

pktBuffer[1024];
MIDIPacketList *pktList = (MIDIPacketList*)pktBuffer;
MIDIPacket *pktPtr = MIDIPacketListInit(pktList);
MIDITimeStamp midiTime = mach_absolute_time();
Byte midiDataToSend[] = {0x91, 0x3c, 0x40};
pktPtr = MIDIPacketListAdd(pktList, sizeof(pktList), pktPtr, midiTime, sizeof(midiDataToSend), midiDataToSend);