Confused about server setup - C# Custom Server, Unity Client

@Sim Basically, however you set up your server (I'd recommend reading the Getting Started Guide for Mirror to get acquainted with how Unity servers work), you don't even really need to consider PlayFab or hosting or any of that until you have a client/server and can connect them both.

Here's an example of how we'd set up a simple client/server architecture using UNET or Mirror (there are many ways to do networking in Unity, but this is what we use):

ExampleScript.cs:

//commands are called on the server
[Command]
public void CmdAddPlayerItem (Player player, Item newItem) {
    player.AddItem(newItem);
}

//rpcs are called on clients, target rpcs are only called on specific (target) clients
[TargetRpc]
public void TargetUpdateScore (NetworkConnection connection, int newScore) {
    this.score = newScore;
}

//on the client:
void ClickOnItem(Item clickedItem) {
    CmdAddPlayerItem(this, clickedItem);
}

//on the server:
void UpdateClientScore(int score) {
    TargetUpdateScore(connectionToClient, score);
} 

The main point is, once you can connect your client to your server with an IP and Port, then you can host it on PlayFab and connect to it