Download DiddyMidiThru here.
DiddyMidiThru, uses Apple’s Bonjour (zeroconf ) to advertise the Midi Service to DiddyMidiDJ. Make sure your firewall is inactive if you have problems connecting.
Download the application and install it in a folder of your choice. Open the application, it should appear in your Dock. You can then open the Midi Receiving app of your choice, such as Traktor Pro. It should be listed in the midi destinations section in whatever manner that application displays it.
Currently DiddyMidiThru outputs on Midi Channel 1 only.