Turn-Based Games: RPC's

What are RPC calls?

A Remote Procedure Call (RPC), simply explained, is when you call code on a different computer than your own, without the need to declare the address of the other computer.

This procedure is commonly used in Server - Client communications, and requires some form of request-response message passing between the two communicating bodies.

How to use RPC calls using Elympics

Luckily for us, Elympics SDK has RPC calls included by default! All you need to do is add an attribute to your method to indicate if it's an RPC call or not.

There are 2 types of RPC calls for Server - Client communications:

[ElympicsRpc(ElympicsRpcDirection.PlayerToServer)]
[ElympicsRpc(ElympicsRpcDirection.ServerToPlayers)]

Limitations of using RPC calls

You can only send primitive data types in RPC calls.

This limitation comes from how communication protocols work over a network.

If you want to send non-primitive types you will need to serialize them in the parameter and deserialize them in the method data.
In the sample code below, you can see how I used JsonUtility which is a class provided by Unity in order to serialize my NonPrimitiveType into a json string.
Then we can easily deserialize it on the Server in the SendNonPrimitiveTypeToServer RPC call.

    [Serializable]
    private struct NonPrimitiveType
    {
        public string s;
        public int i;
    }

    private void DoSomething()
    {
        NonPrimitiveType nonPrimitiveType = new()
        {
            s = "string",
            i = 10,
        };

        string serializedNonPrimitiveType = JsonUtility.ToJson(nonPrimitiveType);
        SendNonPrimitiveTypeToServer(serializedNonPrimitiveType);
    }

    [ElympicsRpc(ElympicsRpcDirection.PlayerToServer)]
    public void SendNonPrimitiveTypeToServer(string serializedData)
    {
        NonPrimitiveType nonPrimitiveType = JsonUtility.FromJson<NonPrimitiveType>(serializedData);
    }

note

You most likely need to add [Serializable] attribute to the struct or class you wish to serialize.

You can only use Elympics RPC's within the ElympicsUpdate() loop or Initialize() method

This limitation comes from the Elympics SDK, as we enable prediction by default. RPC calls could influence states and make prediction impossible.

In order to remove this limitation, you need to disable Prediction in the ElympicsConfig

warning

If you previously implemented synchronization with prediction enabled, this will most likely break your implementation

Now that you understand what RPC calls are, and the limitations, let's go back to Solitaire 21 and how to correctly implement RPC calls.