The man pages and programmer documentations for the socket options SO_REUSEADDR and SO_REUSEPORT are different for different operating systems and often highly confusing. Some operating systems don't even have the option SO_REUSEPORT. The WEB is full of contradicting information regarding this subject and often you can find information that is only true for one socket implementation of a specific operating system, which may not even be explicitly mentioned in the text.

So how exactly is SO_REUSEADDR different than SO_REUSEPORT?

Are systems without SO_REUSEPORT more limited?

And what exactly is the expected behavior if I use either one on different operating systems?