Any site that only serves HTTP/2 content will return a 301 HTTP response code.
It will return a 301 trying to redirect you to HTTP/2 on the same address and port.
Any status code other than 200 will be reported back to the user without any additional processing.
The output of the program will contain the unique number of external resources.
If two files are referenced from abc.com they will only count as one external reference.
Any reference that shares the same base URL will count once.
A full list of references will also be printed out regardless of the uniqueness.
No additional dependencies are required to run the program.