SignalR 从控制器 ASP.NET Core 2.1 调用特定客户端

Question

用户在浏览器中提交表单后，我需要从服务器向客户端发送即时消息。

我按照 Microsoft 的步骤 here 设置了 signalR 连接，创建了集线器 class、signalr.js 等

问题是我只能向所有客户端调用消息，但我需要向发起请求的特定调用者调用消息（否则每个人都会收到消息）。

这是我在 HomeController.cs 中的 POST 操作：

[HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> Submit(string signalRconnectionId, Dictionary<string, string> inputs)
    {
        //Invoke signal to all clients sending a message to initSignal WORKS FINE
        await _signalHubContext.Clients.All.SendAsync("initSignal", "This is a message from the server!");

        //Invoke signal to specified client where signalRConnectionId = connection.id DOES NOT WORK
        await _signalHubContext.Clients.Client(signalRconnectionId).SendAsync("initSignal", "This is a message from server to this client: " + signalRconnectionId);

        return RedirectToAction("Success", inputs);
    }

我的客户javascript 文件：

    //Create connection and start it
const connection = new signalR.HubConnectionBuilder()
    .withUrl("/signalHub")
    .configureLogging(signalR.LogLevel.Information)
    .build();
connection.start().catch(err => console.error(err.toString()));

console.log("connectionID: " + connection.id);
$("#signalRconnectionId").attr("value", connection.id);

//Signal method invoked from server
connection.on("initSignal", (message) => {

    console.log("We got signal! and the message is: " + message);


});

我已经尝试调试操作方法，我正确地传入了“0”的 connectionId（每个连接递增 1）

Answer 1

根据 Microsoft 的说法，您无法从集线器外部访问 ConnectionId 和 Caller https://docs.microsoft.com/en-us/aspnet/core/signalr/hubcontext?view=aspnetcore-2.1

When hub methods are called from outside of the Hub class, there's no caller associated with the invocation. Therefore, there's no access to the ConnectionId, Caller, and Others properties.

Answer 2

这是我根据

的答案得出的最终解决方案

我通过从客户端调用 Hub class 获得了 connectionId，然后从客户端调用传入 connectionId 的控制器。

中心 class:

public class SignalHub : Hub
{
    

    public string GetConnectionId()
    {
        return Context.ConnectionId;
    }
}

客户端javascript启动时执行的代码：

connection.start().catch(err => console.error(err.toString())).then(function(){
connection.invoke('getConnectionId')
    .then(function (connectionId) {
        // Send the connectionId to controller
        console.log("connectionID: " + connectionId);
        $("#signalRconnectionId").attr("value", connectionId);
    });
});

HomeController.cs:

public async Task<IActionResult> Submit(string signalRconnectionId, Dictionary<string, string> inputs)
    {
        
        //Invoke signal to specified client WORKS NOW
        await _signalHubContext.Clients.Client(signalRconnectionId).SendAsync("initSignal", "This is a message from server to this client: " + signalRconnectionId);

        return RedirectToAction("Success", inputs);
    }

它工作正常，但仍然感觉有点像往返，如果我们不必通过枢纽 class 来实现它会更容易。也许只是从客户端开始使用 connectionId，但也许有一个很好的设计理由:)

SignalR 从控制器 ASP.NET Core 2.1 调用特定客户端

SignalR call to specific client from controller ASP.NET Core 2.1

c#

asp.net-mvc

asp.net-core

asp.net-core-signalr