使用 SignalR 向客户端发送消息

Question

I'm trying to send a message from the server to a specific client.

This is my client class (console application)

    static void Main(string[] args)
    {
        var connection = new HubConnectionBuilder()
            .WithUrl("https://localhost:5001/chathub")
            .Build();

        connection.StartAsync().Wait();
        connection.On("ReceiveMessage",(string message) =>
        {
            Console.Write(message);               
        });

        Console.ReadLine();
    }

My HubClass (asp.net mvc core)

public class ChatHub : Hub
{
    public static ConcurrentDictionary<string, MyUserType> MyUsers = new ConcurrentDictionary<string, MyUserType>();

    public Task SendMessageToAll(string message)
    {
        return Clients.All.SendAsync("ReceiveMessage", message);
    }

    public Task SendMessageToUser(string connectionId, string message)
    {
        return Clients.Client(Context.ConnectionId).SendAsync("ReceiveMessage", message);
    }

    public override async Task OnConnectedAsync()
    {
        MyUsers.TryAdd(Context.ConnectionId, new MyUserType() { ConnectionId = Context.ConnectionId });

        await Clients.All.SendAsync("UserConnected", Context.ConnectionId);
        await base.OnConnectedAsync();
    }

    public override async Task OnDisconnectedAsync(Exception ex)
    {
        MyUserType garbage;
        MyUsers.TryRemove(Context.ConnectionId, out garbage);

        await Clients.All.SendAsync("UserDisconnected", Context.ConnectionId);
        await base.OnDisconnectedAsync(ex);
    }
}

public class MyUserType
{
    public string ConnectionId { get; set; }
}

Now how do I execute the Console.Write(message); in the console application from the web app?

I've tried doing something like this:

ChatHub chatHub = new ChatHub();
chatHub.SendMessageToAll("test");

but the Clients is null in the ChatHub class.

Answer 1

You can do something like below in your server:

public class HomeController : Controller
{
    private readonly IHubContext<ChatHub> _hubContext;      
    public HomeController(IHubContext<ChatHub> hubContext)
    {
       _hubContext = hubContext;
    }

    public IActionResult CallClient()
    {
        //execute the client code
        _hubContext.Clients.All.SendAsync("ReceiveMessage", "test");
    }
}