Hi. I'm currently making a building game and I want to know if your friends can join you into a reserved server. Because I have no friends that listen to my messages, I came here to ask. I'm still building the private server system, so I can't test yet.
Technically you cannot unless you have some sort of code or table like local AllowedPlayers = {blah blah} and then allowing like that. Also you could create a party or invite system. Maybe a unlock or lock system. Also your question does not include your code or anything trying to solve the problem other than asking the community for answers. Also some other Scripting Helpers have put answers on your question with API Wiki pages from Roblox. Look at those for refrence and good luck.