I give up.
I'm always searching the Internet and Minecraft.net the program to host Minecraft server on my PC… And I just can't find it. I had found it schonmal, synonymous schonmal downloaded, but deleted it again. And I do not know where it is now.
You can easily download it in the launcher. However, if you want better performance and exciting plugins for your server, I would recommend Spigot to you.
If you are not able to download the Headless from Minecraft then you should leave this with the server…
But to help you: https://mcversions.net/
There are all Minecraft Server jars for all versions