How to connect px4 sitl via udp client

Hi. I am trying to connect to px4 in simulation by jmavsim by udp and I don’t know any idea how to do it.
I am studying mission planner solution, but I am beginner programmer and it is difficult to me to find how establishing connection works inside solution as large as mission planner is.

I will be really grateful if someone show me where I should looking for it.

First, ArduPilot is a different project than PX4, so be aware there may be subtle incompatibilities.

Second, what programming language do you want to work with?

And third I suggest you check out the PX4 MAVSDK;

They even have a nice guide with some example code;