如何向单个客户端发送 SignalR 消息？

Question

对于我的生活，我无法弄清楚如何将 SignalR 消息仅发送给点击“开始”按钮的客户端，而没有其他人。当我将它发送到“All”时一切正常，但我不知道如何在服务器上获取 connectionID，然后将消息发送到启动客户端。这就是我迄今为止的工作。如果您能告诉我如何仅使用调用客户端来完成这项工作，我将不胜感激 -

这是我的 Default.aspx 文件

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="SignalR5._Default" %>

<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server">

    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
            <div><br /><br />
                <asp:Button ID="btnGo" runat="server" Text="GO!!!" OnClick="btnGo_Click" OnClientClick="this.disabled=true;" UseSubmitBehavior="false" /><br /><br />
                <asp:Label ID="lblLog" class="#log" runat="server" Text="Begin"></asp:Label> <br /> <br />
                <asp:Label ID="lblConnectionID" runat="server" Text=""></asp:Label>
            </div>
        </ContentTemplate>
    </asp:UpdatePanel>

    <script src="Scripts/jquery-3.4.1.js"></script>
    <script src="Scripts/jquery.signalR-2.4.2.js"></script>
    <script src="signalr/hubs"></script>

    <script type="text/javascript">
        $(function() {   

            var logger = $.connection.logHub;

            logger.client.logMessage = function(msg) {

                $("#MainContent_lblLog").html(msg);
            };

            $.connection.hub.start().done(function () {
                var cid = $.connection.hub.id;
                $("#MainContent_lblConnectionID").text("ConnectionID: " + cid);
                //alert("connection Id:" + cid);
            });
        });

    </script>
</asp:Content>

这是我的 Default.aspx.cs 文件

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Threading;
using System.Diagnostics;

namespace SignalR5
{
    public partial class _Default : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void btnGo_Click(object sender, EventArgs e)
        {
            //The timer is just to display how long each task takes.
            Stopwatch stopWatch = new Stopwatch();
            stopWatch.Start();
            
            string strMessage = "Hello ";
            LogHub.SendMessage(strMessage);
            Thread.Sleep(2000);
            strMessage += "(" + stopWatch.Elapsed.Seconds + " Seconds)<br>what's up bro? ";

            stopWatch.Restart();
            LogHub.SendMessage(strMessage);
            Thread.Sleep(2500);
            strMessage += "(" + stopWatch.Elapsed.Seconds + " Seconds)<br>Call me soon ";

            stopWatch.Restart();
            LogHub.SendMessage(strMessage);
            Thread.Sleep(3200);
            strMessage += "(" + stopWatch.Elapsed.Seconds + " Seconds)<br>See you later ";

            stopWatch.Restart();
            LogHub.SendMessage(strMessage);
            Thread.Sleep(1800);
            strMessage += "(" + stopWatch.Elapsed.Seconds + " Seconds)<br>Okay man. See you ";

            stopWatch.Restart();
            LogHub.SendMessage(strMessage);
            Thread.Sleep(2900);
            strMessage += "(" + stopWatch.Elapsed.Seconds + " Seconds)<br>We're all Done!";
            lblLog.Text = strMessage;
            
            stopWatch.Stop();
        }
    }
}

这是我的 Startup1.cs 文件

using Microsoft.Owin;
using Owin;
using System;
using System.Threading.Tasks;

[assembly: OwinStartup(typeof(SignalR5.Startup1))]

namespace SignalR5
{
    public class Startup1
    {
        public void Configuration(IAppBuilder app)
        {
            app.MapSignalR();
        }
    }
}

这是我的 LogHub.cs 文件

using Microsoft.AspNet.SignalR;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace SignalR5
{
    public class LogHub : Hub
    {
        // This is the only one working, but I don't want to send to all clients. 
        public static void SendMessage(string strMessage)
        {
            var hub = GlobalHost.ConnectionManager.GetHubContext("LogHub");
            hub.Clients.All.logMessage(strMessage);
   
        }
    }
}

正如我所提到的，我很难弄清楚如何将其发送给“调用者”客户端。它适用于“所有”。

Answer 1

当调用你的“Go”按钮时，你应该调用服务器中的“Go”方法，然后你就可以将数据发送到Caller，比如：

await hub.Clients.Caller.logMessage(message);

Answer 2

连接到 SignalR 集线器的每个客户端都有一个唯一的连接 ID。我们可以使用集线器上下文的 Context.ConnectionId 属性来检索它。使用它，我们可以只向那个特定的客户端发送消息。 Learn more about this here.

因此，要向特定客户端发送消息，您将需要他们的连接 ID 来识别您要将消息发送到哪个客户端。

我在这里做了一个演示，用于向特定用户发送消息。这是集线器类。这个 send 方法会像往常一样向所有连接的客户端发送消息，但我做的额外的事情是，在开始时注册他们的连接 ID 和用户名，以便我以后可以访问它们。

public static class UserHandler
    {
        // just remember when you will restart the app, object will get reset
        public static HashSet<string> ConnectedIds = new HashSet<string>();
        public static HashSet<string> ConnectedUsers = new HashSet<string>();
    }

 public void Send(string name, string message)
        {
            // registering the users
            UserHandler.ConnectedIds.Add(Context.ConnectionId);
            UserHandler.ConnectedUsers.Add(name);

            // Call the broadcastMessage method to update clients.
            Clients.All.broadcastMessage(name, message);
        }

这个SendToSingleUser 方法用于向特定用户发送消息，至于虚拟目的，我只是从列表中随机抽取第一个客户端。如果您已经知道要将它发送给哪个用户，那么您可以将 id 传递给方法并在连接列表中查找 Id 以确保它是有效的连接。

public void SendToSingleUser(string userName, string message)
        {

            string fromUserId = Context.ConnectionId;
            //removing the currrent user ID & name
            UserHandler.ConnectedIds.Remove(fromUserId);
            UserHandler.ConnectedUsers.Remove(userName);

            //taking a random user for sending message
            string toUserId = UserHandler.ConnectedIds.First();
            string toUserName = UserHandler.ConnectedUsers.First();

            if (toUserId != null && fromUserId != null)
            {
                // send to 
                Clients.Client(toUserId).sendPrivateMessage(userName, message);

                // send to caller user
                Clients.Caller.sendPrivateMessage(userName, message);
            }

        } 

aspx 文件：

    <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Chat.aspx.cs" Inherits="SignalRChat.Chat" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>SignalR Chat : Chat Page</title>

    <link href="Content/bootstrap.css" rel="stylesheet" />
    <link href="Content/style.css" rel="stylesheet" />
    <link href="Content/font-awesome.css" rel="stylesheet" />

    <script src="Scripts/jQuery-1.9.1.min.js"></script>
    <script src="Scripts/jquery.signalR-2.2.2.min.js"></script>
    <script src="Scripts/date.format.js"></script>
    <!--Reference the autogenerated SignalR hub script. -->
    <script src="signalr/hubs"></script>


    <script type="text/javascript">

        $(function () {

            // Declare a proxy to reference the hub. 
            var chat = $.connection.chatHub;
            // Create a function that the hub can call to broadcast messages.
            chat.client.broadcastMessage = function (name, message) {
                // Html encode display name and message. 
                var encodedName = $('<div />').text(name).html();
                var encodedMsg = $('<div />').text(message).html();
                // Add the message to the page. 
                $('#discussion').append('<li><strong>' + encodedName
                    + '</strong>:&nbsp;&nbsp;' + encodedMsg + '</li>');
            };

            // Create a function that the hub can call to broadcast private messages
            chat.client.sendPrivateMessage = function (name, message) {
                // Html encode display name and message. 
                var encodedName = $('<div />').text(name).html();
                var encodedMsg = $('<div />').text(message).html();
                // Add the message to the page. 
                $('#discussion').append('<li><strong>' + encodedName
                    + '</strong>:&nbsp;&nbsp;' + encodedMsg + '</li>');
            };


            // Get the user name and store it to prepend to messages.
            $('#displayname').val(prompt('Enter your name:', ''));
            $('#CurrentUser').append($('#displayname').val());
            // Set initial focus to message input box.  
            $('#message').focus();
            // Start the connection.
            $.connection.hub.start().done(function () {

                //send to all user
                $('#sendmessage').click(function () {

                    var msg = $("#message").val();

                    if (msg.length > 0) {
                        debugger;
                        var userName = $('#displayname').val();
                        chat.server.send(userName, msg);
                        $('#message').val('').focus();
                    }
                });

                //send to a sepcific user
                $('#sendToSingleUser').click(function () {

                    var msg = $("#message").val();

                    if (msg.length > 0) {
                        debugger;
                        var userName = $('#displayname').val();
                        chat.server.sendToSingleUser(userName, msg);
                        $('#message').val('').focus();
                    }
                });
            });
        });

    </script>

</head>
<body>
    <form id="form1" runat="server">
        <asp:ScriptManager ID="ScriptManager1" runat="server" ></asp:ScriptManager>
        <div class="content-wrapper">
            <div class="row">
                 <div class="container">
                    <label id="CurrentUser"> </label>
                    <input type="text" id="message" />
                    <input type="button" id="sendmessage" value="Send" />
                    <input type="button" id="sendToSingleUser" value="Send Single User" />
                    <input type="hidden" id="displayname" />
                    <ul id="discussion">
                    </ul>
                </div>
            </div>
        </div>

         <script src="Scripts/bootstrap.min.js"></script>

    </form>
</body>
</html>

完整的演示可以在here找到

注意：此演示与您发布的示例不同，我只是想告诉您如何实现通信。