How to do rewrite in htaccess from a folder to another domain port?

Question

Apache HTTP Server

There is a site, somedomain
When requesting
somedomain/a , it is necessary to send a request to the address
somedomain:81
+ if a redirect occurs in the somedomain:81/redirectpath code, you need to send it to
somedomain/a/redirectpath (again, so that it sends everything without client participation to 81 port)
Is it possible to do this?
GET and POST

Why? For the evil admin does not open other ports, except for 80.
PS in all links, a slash at the end, that one cuts.
redirectpath can be anything

Answer 1

You need to talk to the evil admin ;)
Or, as an option, use 3rd level domains so that they are free ;)
and hang all your household on port 80