if you just rent a windows server used as remote desktop PC, there is no need ICP. In another words, if there is no ICP bind on the server you have, port 80 will be blocked, 3389 ( windows remote desktop ) is still open, and you could login in the windows server by windows remote desktop, and open any browser to browse website like a PC locating in China.

Only when you run a content distribution platform (like a website, chat room etc).

Other than that, you're mostly fine without an ICP (Internet Content Provider) license.

Only TCP port 80 and 443 requires ICP.

If you just build a service for yourself only, you do not need ICP