PX4 and QGC MAVLink Comm

I’m doing a simple cmdline app in C#.
I’ve managed to use a TCP Listener to PX4 in SITL send/receive HEARTBEAT fine.
Then from QGC.
Should my app also connect to UDP:14540 and send the same messages I send to PX4 SITL?
Or I just communicate with PX4 and it will proxy everything to me into QGC?