Luckily for you, Ethernet is bidirectional. If you type a link, the rj45-port is output. If you receive an answer (a webpage) it's input. So - whatever other problems you might encounter, and I'm afraid it will be an unsurmountable lot - not an rj45 port doesn't do output.
I want to use some software to block adults websites and other stuff on my home internet.
I'm planning to buy a usb 3.0 to rj45 and connect the usb to the laptop and the rj45 to the modem.
after that, I want to connect the laptop to a router so every computer in my house could connect to my router with a safe internet.
The problem is - I do not know how to make my old laptop using the rj45 as an output and not as an input (because I want it to transmit the data from the modem to the router.
I know it is not a server but I want it to work in the same way - so how can I do that?