namespace SingralRedis.Hubs
{
    interface IChatHub
    {
        //服务器下发消息到各个客户端
        void SendChat(string id, string name, string message);

        //用户上线通知
        void SendLogin(string id, string name);

        //用户下线通知
        void SendLogoff(string id, string name);

        //接收客户端发送的心跳包并处理
        void TriggerHeartbeat(string id, string name);
    }
}

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


namespace SingralRedis.Hubs
{
    public class ChatHub : Hub,IChatHub
    {

        public override System.Threading.Tasks.Task OnConnected()
        {

            string userName = Context.QueryString["userName"]; //获取客户端发送过来的用户名
            string userId = Context.QueryString["userId"]; //获取客户端发送过来的用户名
            string connectionId = Context.ConnectionId;
            if (!string.IsNullOrEmpty(userId))
            {
                SendLogin(userId, userName, connectionId);
            }
            //HttpContext.Current.Application.Add(userName, connectionId); //存储关系
            return base.OnConnected();
        }
        public class UserChat
        {
            public UserChat()
            {
                Count = 0;
                if (Timer == null) Timer = new Timer();
                Timer.Interval = 1000;  //1s触发一次
                Timer.Start();
                Timer.Elapsed += (sender, args) =>
                {
                    Count++;
                    if (Count >= 20)
                    {
                        action();  //该用户掉线了，抛出事件通知
                        Timer.Stop();
                    }
                };
            }

            private readonly Timer Timer;
            public event Action action;
            //public event Action action1;

            public string UserId { get; set; }
            public string ID { get; set; }
            public string Name { get; set; }

            //内部计数器（每次递增1），如果服务端每5s能收到客户端的心跳包，那么count被重置为0；
            //如果服务端20s后仍未收到客户端心跳包，那么视为掉线
            public int Count { get; set; }
        }

        public static class ChatUserCache
        {
            public static IList<UserChat> userList = new List<UserChat>();
        }

        private IList<UserChat> userList = ChatUserCache.userList;       
       
        /// <summary>
        /// 推送个单个用户
        /// </summary>
        /// <param name="name">用户名</param>
        public void SendToUser(string name)
        {
            //根据username获取对应的ConnectionId
            var user = userList.FirstOrDefault(v => v.Name == name);
            if (user != null)
            {
                Clients.Client(user.UserId).addNewMessageToPage("新的信息");
            }
        }

        /// <summary>
        /// 自发自收
        /// </summary>
        public void ReturnId()
        {
            Clients.Caller.CheckId(Context.ConnectionId);
        }    

        /// <summary>
        /// 获取全部用户
        /// </summary>
        public void GetAllUserList()
        {
            Clients.All.loginUser(userList);
        }



        public void SendChat(string id, string name, string message)
        {
            Clients.Client(id).GetChatMsg("<====用户 " + name +" 发送消息 "+ message+" ======>");
            
        }

        public void SendLogin(string id, string name, string connectionId)
        {
            connectionId = string.IsNullOrEmpty(connectionId) ? connectionId = Context.ConnectionId : connectionId;

            if (!userList.Any(v => v.ID == id))
            {
                var userInfo = new UserChat() { UserId = connectionId, ID = id, Name = name };
                userInfo.action += () =>
                {
                    //用户20s无心跳包应答，则视为掉线，会抛出事件，这里会接住，然后处理用户掉线动作。
                    SendLogoff(id, name);
                };
                userList.Add(userInfo);
            }
            else
            {
                var user = userList.FirstOrDefault(v => v.ID == id);
                user.UserId = connectionId;
                user.Count = 0;
            }
            Clients.All.loginUser(userList);
            
        }

        public void SendLogoff(string id, string name)
        {
            var userInfo = userList.Where(x => x.ID.Equals(id) && x.Name.Equals(name)).FirstOrDefault();
            if (userInfo != null)
            {
                var name1 = userInfo.Name;

                if (userList.Remove(userInfo))
                {
                    Clients.All.logoffUser(userList);


                    SendChat(id, name, "<====用户 " + name + " 退出了讨论组====>");
                }
            }
        }

        public void TriggerHeartbeat(string id, string name)
        {
            var userInfo = userList.Where(x => x.ID.Equals(id) && x.Name.Equals(name)).FirstOrDefault();
            if (userInfo != null)
            {
                userInfo.Count = 0;  //收到心跳，重置计数器
            }
        }
    }
}