Running Gazebo and PX4 SITL in different machines

Thanks for the command to run gazebo headless, very useful, I had resorted to killing gzclient everytime!

I’m having no luck however with the broadcast.

PX4 blocks with this message:

INFO [simulator] Waiting for initial data on UDP port 14560. Please start the flight simulator to proceed..

Do I have to do something equivalent on the gazebo side?
Is gazebo broadcasting too by default? or sending to localhost?

Thanks