【发布时间】：2020-03-08 00:27:50
【问题描述】：
我非常接近在 C# 中实现一个系统，它允许我通过单击按钮从用 ASP.net 编写的界面向充当客户端的 C# 控制台应用程序发送推送通知。这一切都使用 WebSockets。
阅读大量教程并重用网上找到的代码后，我已经能够成功建立 WebSocket 连接。我还不能真正发送通知。
我正在努力解决的部分是单击按钮后立即触发的功能：
//Close ticket and send push-notification over websocket
public void Close(int id) {
//Ticket ticket = mgr.GetTicket(id);
//Create a new notification
Notification notif = new Notification();
notif.message = "Rofl test123 Notification lol";
//Initialize WebSocketMiddleware here??
//WebSocketsMiddleware wsm = new WebSocketsMiddleware(what parameter??);
//wsm.Invoke(what HttpContext parameter???)
NotificationManager notifMgr;
//notifMgr.AddSubscriber(wsm);
//notifMgr.SendNotificationAsync(notif);
return;
}
我遇到的具体问题/问题是：
- 如何初始化类WebSocketsMiddleware？是否需要初始化，如果需要，RequestDelegate类型的参数是什么？我应该向该参数传递什么？
- WebSocketsMiddleware 有一个带有 HttpContext 类型参数上下文的 Invoke 函数。我只需要将
new HttpContext()传递给这个吗？够了吗？ - 有人做了一个类NotificationManager，这个类使用中间件来实际发送通知。我是否只需将初始化的 WebSocketsMiddleware 变量作为 NotificationManager.AddSubscriber() 的参数传递？那么每个客户端的通知会被很好地分开吗？
- 之后我可以使用 SendNotificationAsync() 发送通知吗？
- 额外问题：假设每个客户都有自己的按钮。当我单击客户的按钮时，只有该客户可能会收到推送通知。如何确保所有其他客户也不会收到相同的通知？
为了能够帮助我解决这些问题，您需要以下课程。问题只是关于 WebSockets，更多的是关于如何启动和使用我从教程中收集的类。
Notification.cs - 表示通知的类（通知文本、发送日期...）：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace SC.UI.MVC.Models
{
public class Notification
{
public Guid? notificationId { get; set; }
public int id { get; set; }
public DateTime timestamp { get; set; }
public string message { get; set; }
public string type { get; set; }
public Notification()
{
// add a new guid as a unique identifier for the notification in the db
notificationId = Guid.NewGuid();
}
}
}
WebSocketsMiddleware.cs - 处理 WebSocket 的低级部分，调用连接等：
using Microsoft.AspNetCore.Http;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.WebSockets;
using System.Threading;
using System.Threading.Tasks;
namespace NotificationsApi.Notifications
{
public class WebSocketsMiddleware
{
// private variable to track the next delegate to call in the request chain
private readonly RequestDelegate _next;
public WebSocketsMiddleware(RequestDelegate next)
{
_next = next;
}
public async Task Invoke(HttpContext context)
{
CancellationToken ct = context.RequestAborted;
string currentSubscriberId = null;
WebSocket currentSocket = null;
// we want to listen on a specific path for websocket communications
if (context.Request.Path == "/notifications/ws")
{
// make sure the request is a websocket request
if (context.WebSockets.IsWebSocketRequest)
{
currentSocket = await context.WebSockets.AcceptWebSocketAsync();
currentSubscriberId = NotificationManager.Instance.AddSubscriber(currentSocket);
// keep the socket open until we get a cancellation request
while (true)
{
if (ct.IsCancellationRequested)
{
break;
}
}
}
else // return an HTTP bad request status code if anything other a web socket request is made on this URI
{
context.Response.StatusCode = 400;
}
}
// clean up the socket
if (!string.IsNullOrWhiteSpace(currentSubscriberId))
{
NotificationManager.Instance.RemoveSubscriber(currentSubscriberId);
if (currentSocket != null)
{
await currentSocket.CloseOutputAsync(WebSocketCloseStatus.NormalClosure, "Closing", CancellationToken.None);
currentSocket.Dispose();
}
}
// call the next delegate in the pipeline
await _next(context);
return;
}
}
}
NotificationManager.cs - 具有添加和删除订阅者以及实际发送通知的三个功能的接口/类。使用 WebSocket 中间件来实现：
using SC.UI.MVC.Models;
//using NotificationsApi.Persistence;
using Newtonsoft.Json;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Net.WebSockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
namespace NotificationsApi.Notifications
{
// interface for NotificationManager for dependency injection
public interface INotificationManager
{
string AddSubscriber(WebSocket subscriber);
void RemoveSubscriber(string subscriberId);
Task SendNotificationAsync(Notification notification);
}
public class NotificationManager : INotificationManager
{
// static instance of the NotificationManager class
private static INotificationManager _instance;
public static INotificationManager Instance { get { return _instance ?? (_instance = new NotificationManager()); } set { _instance = value; } }
// static dictionary to keep track of all notification subscribers
private static ConcurrentDictionary<string, WebSocket> _subscribers = new ConcurrentDictionary<string, WebSocket>();
// adds a subscriber to receive notifications
public string AddSubscriber(WebSocket subscriber)
{
var subscriberId = Guid.NewGuid().ToString();
_subscribers.TryAdd(subscriberId, subscriber);
return subscriberId.ToString();
}
// removes a notifications subscriber
public void RemoveSubscriber(string subscriberId)
{
WebSocket empty;
_subscribers.TryRemove(subscriberId, out empty);
}
// sends a notification to all subscribers
public async Task SendNotificationAsync(Notification notification)
{
// add the notification to the persistence store
//await PersistenceManager.Instance.AddNotificationAsync(notification);
// send the notification to all subscribers
foreach (var s in _subscribers)
{
if (s.Value.State == WebSocketState.Open)
{
var jsonNotification = JsonConvert.SerializeObject(notification);
await SendStringAsync(s.Value, jsonNotification);
}
}
}
// sends a string via web socket communication
private async Task SendStringAsync(WebSocket socket, string data, CancellationToken ct = default(CancellationToken))
{
var buffer = Encoding.UTF8.GetBytes(data);
var segment = new ArraySegment<byte>(buffer);
await socket.SendAsync(segment, WebSocketMessageType.Text, true, ct);
}
}
}
Client.cs - 接收推送通知的客户端。我猜这里不是问题：
/* WEBSOCKET PART */
//Variables for websocket
private static object consoleLock = new object();
private const int sendChunkSize = 256;
private const int receiveChunkSize = 256;
private const bool verbose = true;
private static readonly TimeSpan delay = TimeSpan.FromMilliseconds(30000);
//Function to check if a ticket from this client is closed/solved
public void checkTicketSolved() {
Thread.Sleep(1000);
Connect("ws://localhost:5050/notifications/ws").Wait();
Console.WriteLine("Press any key to exit...");
}
public static async Task Connect(string uri)
{
ClientWebSocket webSocket = null;
try
{
webSocket = new ClientWebSocket();
await webSocket.ConnectAsync(new Uri(uri), CancellationToken.None);
await Task.WhenAll(Receive(webSocket), Send(webSocket));
}
catch (Exception ex)
{
Console.WriteLine("Exception: {0}", ex);
}
finally
{
if (webSocket != null)
webSocket.Dispose();
Console.WriteLine();
lock (consoleLock)
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine("WebSocket closed.");
Console.ResetColor();
}
}
}
static UTF8Encoding encoder = new UTF8Encoding();
private static async Task Send(ClientWebSocket webSocket)
{
//byte[] buffer = encoder.GetBytes("{\"op\":\"blocks_sub\"}"); //"{\"op\":\"unconfirmed_sub\"}");
byte[] buffer = encoder.GetBytes("{\"op\":\"unconfirmed_sub\"}");
await webSocket.SendAsync(new ArraySegment<byte>(buffer), WebSocketMessageType.Text, true, CancellationToken.None);
while (webSocket.State == WebSocketState.Open)
{
LogStatus(false, buffer, buffer.Length);
await Task.Delay(delay);
}
}
private static async Task Receive(ClientWebSocket webSocket)
{
byte[] buffer = new byte[receiveChunkSize];
while (webSocket.State == WebSocketState.Open)
{
var result = await webSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);
if (result.MessageType == WebSocketMessageType.Close)
{
await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
}
else
{
LogStatus(true, buffer, result.Count);
}
}
}
private static void LogStatus(bool receiving, byte[] buffer, int length)
{
lock (consoleLock)
{
Console.ForegroundColor = receiving ? ConsoleColor.Green : ConsoleColor.Gray;
//Console.WriteLine("{0} ", receiving ? "Received" : "Sent");
if (verbose)
Console.WriteLine(encoder.GetString(buffer));
Console.ResetColor();
}
}
}
您也可以在Github 上找到此代码。 相关部分代码位于：
- WebServer/UI-MVC/Controllers/TicketController.cs -> 包含点击按钮时触发的函数。
- WebServer/UI-MVC/Notifications -> 包含 NotificationManager.cs 和 WebSocketsMiddleware.cs
- WebServer/UI-MVC/Models -> 包含 Notification.cs
- Client/ 包含客户端控制台应用程序的所有代码
为您提供有关该应用程序的一些背景信息： 这个应用程序代表一个票务系统，它允许使用我的软件的客户/客户打开支持票。 WebServer 部分供我的管理员/员工回答和管理工单。控制台应用程序是我的客户/客户需要安装的，以便联系我的支持服务并打开支持票证。当管理员通过单击按钮关闭客户的票证时，这意味着票证，因此客户的问题已解决并关闭。导致客户端收到关于此的推送通知。
我不是在寻找有关 WebSockets 的其他教程的参考资料或使用 SignalR 的建议或其他任何东西，我已经阅读了所有这些，并且我已经使用了 SignalR，但现在对纯 WebSockets 感兴趣。如果有人可以帮助我解决此问题中发布的第一部分代码（关闭函数）并解释他所做的事情，我将非常感激。谢谢！
【问题讨论】：
-
用于教育目的。我们必须研究一些具体的技术并实施它们。我选择了 SignalR 和 Websockets。我必须同时使用它们，已经成功实现了 SignalR。现在接近 WebSockets。