Send mavlink commands to px4 without GCS

Hi, we are trying to send our commands manually, so we need to know which udp Port to write to from our aplication

Pixhawk, Cube and other FC boards do not have a UDP port. So I guess you want to write to an Ardupilot SITL instance? If that is the case use pymavlink to generate code that you can use and link in your application to connect and send Mavlink messages to the SITL instance.