Asp.net は SignalR を使用してクールなエンドツーエンド チャット機能を実装します

public interface IHubConnectionContext<T>
{
T All { get; } // 代表所有客户端
 
T AllExcept(params string[] excludeConnectionIds); // 除了参数中的所有客户端
T Client(string connectionId); // 特定的客户端，这个方法也就是我们实现端对端聊天的关键
T Clients(IList<string> connectionIds); // 参数中的客户端端
T Group(string groupName, params string[] excludeConnectionIds); // 指定客户端组，这个也是实现群聊的关键所在
T Groups(IList<string> groupNames, params string[] excludeConnectionIds);
T User(string userId); // 特定的用户
T Users(IList<string> userIds); // 参数中的用户
}

public class ChatHub : Hub
 {
 // 静态属性
 public static List<UserInfo> OnlineUsers = new List<UserInfo>(); // 在线用户列表
 
 /// <summary>
 /// 登录连线
 /// </summary>
 /// <param name="userId">用户Id</param>
 /// <param name="userName">用户名</param>
 public void Connect(string userId, string userName)
 {
  var connnectId = Context.ConnectionId;
 
  if (OnlineUsers.Count(x => x.ConnectionId == connnectId) == 0)
  {
  if (OnlineUsers.Any(x => x.UserId == userId))
  {
   var items = OnlineUsers.Where(x => x.UserId == userId).ToList();
   foreach (var item in items)
   {
   Clients.AllExcept(connnectId).onUserDisconnected(item.ConnectionId, item.UserName);
   }
   OnlineUsers.RemoveAll(x => x.UserId == userId);
  }
 
  //添加在线人员
  OnlineUsers.Add(new UserInfo
  {
   ConnectionId = connnectId,
   UserId = userId,
   UserName = userName,
   LastLoginTime = DateTime.Now
  });
  }
 
  // 所有客户端同步在线用户
  Clients.All.onConnected(connnectId, userName, OnlineUsers);
 }
 
 
 /// <summary>
 /// 发送私聊
 /// </summary>
 /// <param name="toUserId">接收方用户连接ID</param>
 /// <param name="message">内容</param>
 public void SendPrivateMessage(string toUserId, string message)
 {
  var fromUserId = Context.ConnectionId;
 
  var toUser = OnlineUsers.FirstOrDefault(x => x.ConnectionId == toUserId);
  var fromUser = OnlineUsers.FirstOrDefault(x => x.ConnectionId == fromUserId);
 
  if (toUser != null && fromUser != null)
  {
  // send to
  Clients.Client(toUserId).receivePrivateMessage(fromUserId, fromUser.UserName, message);
 
  // send to caller user
  // Clients.Caller.sendPrivateMessage(toUserId, fromUser.UserName, message);
  }
  else
  {
  //表示对方不在线
  Clients.Caller.absentSubscriber();
  }
 }
 
 /// <summary>
 /// 断线时调用
 /// </summary>
 /// <param name="stopCalled"></param>
 /// <returns></returns>
 public override Task OnDisconnected(bool stopCalled)
 {
  var user = OnlineUsers.FirstOrDefault(u => u.ConnectionId == Context.ConnectionId);
 
  // 判断用户是否存在,存在则删除
  if (user == null) return base.OnDisconnected(stopCalled);
 
  Clients.All.onUserDisconnected(user.ConnectionId, user.UserName); //调用客户端用户离线通知
  // 删除用户
  OnlineUsers.Remove(user);
 
 
  return base.OnDisconnected(stopCalled);
 }
 }