How to open mutiple ports in ofxMidi? I only have one port available on a standard mac

// print input ports to console
midiIn.listPorts(); // via instance
//ofxMidiIn::listPorts(); // via static as well

// open port by number (you may need to change this)
midiIn.openPort(0);
//midiIn.openPort("IAC Pure Data In");	// by name
//midiIn.openVirtualPort("ofxMidiIn Input");	// open a virtual port

// don't ignore sysex, timing, & active sense messages,
// these are ignored by default
midiIn.ignoreTypes(false, false, false);

// add testApp as a listener
midiIn.addListener(this);

// print received messages to the console
//midiIn.setVerbose(true);
ofxMidiIn nanoP;
ofxMidiIn nanoK;
//...
ofxMidiIn::listPorts();
//[notice ] ofxMidiIn: 2 ports available
nanoP.openPort(0);
nanoK.openPort(1);
nanoP.addListener(this);
nanoK.addListener(this);