Uploading Flight Plan from custom program

I am trying to send the flight plan through a remote location to the controller. The controller will be connected to a micro computer.
Is it possible that we write our own program that writes the flight plan and upload the flight plan to the controller using UDP protocol.

Please advice where can I find out about such information?

Do you want to send waypoint commands to the controller in real time, or sending preset mission/play/waypoint file to the controller?

Hi, would require sending preset way points. Or make alteration if necessarily. I will be putting a raspberry pi onboard. Hopely I can upload the flight way point directly from raspberry pi to the controller.

If you have a companion computer onboard, you can make programs there and let it control your vehicle.
You may have a look at pymavlink, mavproxy, and dronekit.
They all send mavlink command through serial port to the controller. In this case you can even bypass mission planner.

Hi,
Sounds good, so I connect direction my raspberry pi to the controller using serial and communicate using mavlink?

Hi, Is the microUSB usable for communicating mavlink between my computer and the controller?

I see here it seems that the communication protocol is UDP. So it should be connected within a LAN network?

Please advice if I can communicate using Microusb or is there a way which I connect through a lan router?

Yes. But USB connection is not as reliable as those on carrier board.

You may check how to connect your companion computer to autopilot here:
https://ardupilot.org/dev/docs/companion-computers.html

There are varies connection methods, you may look into the datasheet/docs of each protocols