What do I need in order to make a player-hosted online RPG?

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Hey! I'm interested in making an online RPG, where the servers are hosted by players (Examples of this would be Minecraft/Terraria). This is different from an MMO where you have one big server and everyone connects to it. I'm talking about servers that are run on your own PC and hold up to 50~ people.

I've toying around with PUN but I'm struggling with alot of technical issues, for example:
The combat system is one where players get transferred to a new scene, and a combat sequence commences in a Turn-Based JRPG fashion. Some people might be in the battle sequence, some might not, it depends if they're in the same party. This means I cant sync up with the MasterClient or anything because they might not be in the same battle sequence as the others!

So I saw there are Photon Servers, but is that what I'm looking for? I'm pretty new to all this, so I guess the core of the question is: What services do I need to use in order to make an online RPG like the one I'm describing?
Thanks in advance!