SignalR Real-Time Communication

Hub Definition

public sealed class NotificationHub : Hub
{
    public async Task SendMessage(string user, string message)
    {
        await Clients.All.SendAsync("ReceiveMessage", user, message);
    }

    public async Task JoinGroup(string groupName)
    {
        await Groups.AddToGroupAsync(Context.ConnectionId, groupName);
        await Clients.Group(groupName).SendAsync("UserJoined", Context.UserIdentifier);
    }

    public async Task SendToGroup(string groupName, string message)