public class StreamHub : Hub
    {
        public ChannelReader<string> ReadLogStream()
        {
            var channel = Channel.CreateUnbounded<string>();
            _ = WriteFileLine(channel.Writer);

            return channel.Reader;
        }

        private async Task WriteFileLine(ChannelWriter<string> writer)
        {
            using (var streamReader = new StreamReader(Directory.GetCurrentDirectory() + "/logs/server.log"))
            {
                string line;
                while ((line = streamReader.ReadLine()) != null)
                {
                    await writer.WriteAsync(line);
                    await Task.Delay(TimeSpan.FromSeconds(2));
                }

                writer.TryComplete();
            }
        }
    }
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.SignalR;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace SignalRCharSample.Hubs
{
    [Authorize]
    public class UserChatHub: Hub
    {
        public async Task SendMessage(string toUserName, string message)
        {
            await Clients.User(toUserName).SendAsync("ReceiveMessage", $"{DateTime.Now}--{Context.UserIdentifier}--{message}");
        }
    }
}

　　

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
</head>
<body>
    <div>
        UserName：<input type="text" id="userInput" />
        Message：<input type="text" id="messageInput" />
        <input type="button" id="sendButton" value="Send" />
    </div>
    <ul id="messagesList"></ul>
    <script src="https://localhost:57634/lib/jquery/dist/jquery.js"></script>
    <script src="https://localhost:57634/lib/signalr.min.js"></script>
    <script>
        var connection = new signalR.HubConnectionBuilder().withUrl("https://localhost:57634/chatHub").build();
        connection.on("ReceiveMessage", function (user, message) {
            var msg = user + " says " + message;
            var li = document.createElement("li");
            li.textContent = msg;
            document.getElementById("messagesList").appendChild(li);
        });

        connection.start().catch(function (err) {
            return console.error(err.toString());
        });


        document.getElementById("sendButton").addEventListener("click", function (event) {
            var user = document.getElementById("userInput").value;
            var message = document.getElementById("messageInput").value;
            connection.invoke("SendMessage", user, message).catch(function (err) {
                return console.error(err.toString());
            });

            event.preventDefault();
        });

    </script>
</body>
</html>

using Microsoft.AspNetCore.SignalR;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace SignalRCharSample.Hubs
{
    public class ChatHub : Hub
    {
        public async Task SendMessage(string user, string message)
        {
            await Clients.All.SendAsync("ReceiveMessage", user, DateTime.Now + "--" + message);
        }

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

        public Task SendMessageToGroups(string message)
        {
            List<string> groups = new List<string>() { "Group1","Group2" };
            return Clients.Groups(groups).SendAsync("ReceiveMessage", message);
        }

        public override async Task OnConnectedAsync()
        {
            await Groups.AddToGroupAsync(Context.ConnectionId, "Group1");
            await base.OnConnectedAsync();
        }

        public override async Task OnDisconnectedAsync(Exception exception)
        {
            await Groups.RemoveFromGroupAsync(Context.ConnectionId, "Group1");
            await base.OnDisconnectedAsync(exception);
        }
    }
}
using Microsoft.AspNetCore.SignalR;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace SignalRCharSample.Hubs
{
    public class CustomUserIdProvider : IUserIdProvider
    {
        public string GetUserId(HubConnectionContext connection)
        {
            //return connection.GetHttpContext().Request.Query["userid"];

            return connection.User?.FindFirst("UserName")?.Value;
        }
    }
}
using Microsoft.AspNetCore.SignalR;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace SignalRCharSample.Hubs
{
    public class GroupChatHub: Hub
    {
        public async Task AddToGroup(string groupName)
        {
            await Groups.AddToGroupAsync(Context.ConnectionId, groupName);

            await Clients.Group(groupName).SendAsync("Send", $"{Context.ConnectionId} has joined the group {groupName}.");
        }

        public async Task RemoveFromGroup(string groupName)
        {
            await Groups.RemoveFromGroupAsync(Context.ConnectionId, groupName);

            await Clients.Group(groupName).SendAsync("Send", $"{Context.ConnectionId} has left the group {groupName}.");
        }

        public Task SendMessageToGroup(string groupName, string message)
        {
            return Clients.Group(groupName).SendAsync("Send", $"{Context.ConnectionId}: {message}");
        }

        public override Task OnConnectedAsync()
        {
            return base.OnConnectedAsync();
        }
    }
}