AttributesSync Class

public class AttributesSync : CommunicationBridgeUID

public class MyAttributesSyncClass : AttributesSync
{
       [SynchronizableField]
       public string MyString;
}

public class MessageAll : AttributesSync
{
    public void SendRpc()
    {
        // Invoke method by name. alternatively, we can call by index.
        BroadcastRemoteMethod(nameof(Message), "Hello, world!");
    }

    // the SynchronizableMethod attribute marks methods available for remote invocation.
    [SynchronizableMethod]
    private void Message(string msg)
    {
        Debug.Log(msg);
    }
}

public class PlayAudioSync : AttributesSync
{
    // reference to AudioSource.
    public AudioSource AudioSource;

    // public method that we call in event or from external scripts
    public void Play()
    {
        // Invoke method with index 0 on all clients including sender.
        BroadcastRemoteMethod();
    }

    // We define our synced method here.
    // As we only define one we know this one have index 0.
    [SynchronizableMethod]
    private void PlayRemote()
    {
        AudioSource.Play();
    }
}

public class Message : AttributesSync
{
    // id is index of user
    public void SendMessageToUser(ushort id, string message)
    {
        // Invoke method by index.
        InvokeRemoteMethod(0, id, message);
    }

    public void SendMessageToUser(ushort[] ids, string message)
    {
        // Invoke method by index.
        InvokeRemoteMethod(0, ids, message);
    }

    // Because this is the first method defined, we know its index is 0. The next one would have index of 1.
    [SynchronizableMethod]
    private void Message(string msg)
    {
        Debug.Log(msg);
    }
}