Startup parameters

Startup options for the server (like port to run on) seem to be managed in the predicate server_opts/1. However, I do not use how to use them. Regarding the port option, for instance, neither of the following works:

swipl -s run.pl --port 8976

swipl -s run.pl --port=8976

swipl -s run.pl port=8976

According to the swipl usage message, swi-options and programm arguments should (can?) be separated by --. This seems to kinda work. However, then our code complains that -- is no valid argument.

Basically, I have the following questions:

1. How is it possible to start the server with arguments?
2. Which arguments are defined? Or rather, what do they do?
3. Can we print some usage message ourselves? For example with -h but without interfering with swipl's -h argument?