Asp.net Core中如何使用中間件來管理websocket

來源：懂視網責編：小采時間：2020-11-27 22:34:54

Asp.net Core中如何使用中間件來管理websocket

Asp.net Core中如何使用中間件來管理websocket:介紹我喜歡.NET CORE 這個東西，其實不僅僅源于它性能很高，可以跨平臺，還因為它的設計模式確實令人著迷。以前沒.NET CORE 的時候，.NET用websocket必須跑在windows server 2012上，但我一般不會這么干，都把websocket架在nodejs的服務器上

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導讀Asp.net Core中如何使用中間件來管理websocket:介紹我喜歡.NET CORE 這個東西，其實不僅僅源于它性能很高，可以跨平臺，還因為它的設計模式確實令人著迷。以前沒.NET CORE 的時候，.NET用websocket必須跑在windows server 2012上，但我一般不會這么干，都把websocket架在nodejs的服務器上

介紹

我喜歡.NET CORE 這個東西，其實不僅僅源于它性能很高，可以跨平臺，還因為它的設計模式確實令人著迷。以前沒.NET CORE 的時候，.NET用websocket必須跑在windows server 2012上，但我一般不會這么干，都把websocket架在nodejs的服務器上。這么分出來，麻煩肯定是麻煩的，而且js這東西，寫復雜和幾年后再看都是頭疼的問題。那么，如果.NET CORE是以kestrel運行的，那么就不再需要考慮服務器的版本運行，任何一個地方都可以用websocket

ASP.NET Core SignalR是一個有用的庫，可以簡化Web應用程序中實時通信的管理。但是，我寧愿使用WebSockets，因為我想要更靈活，并且與任何WebSocket客戶端兼容。

在Microsoft的文檔中，我找到了一個很好的WebSockets工作示例。它仍然是管理連接，以便能夠從一個連接向其他連接廣播消息，這是SignalR開箱即用的功能。期望這個邏輯非常復雜，我想從Startup類中刪除它。

背景

要閱讀ASP.NET Core中的WebSockets支持，可以在此處查看。如果您想了解中間件以及如何在ASP.NET Core中編寫它，請閱讀此鏈接。

代碼使用

首先，你必須添加 Microsoft.AspNetCore.WebSockets 包到你的項目。

現在，您可以創建一個擴展方法和類來管理WebSockets：

public static class WebSocketExtensions
{
 public static IApplicationBuilder UseCustomWebSocketManager(this IApplicationBuilder app)
 {
 return app.UseMiddleware<CustomWebSocketManager>();
 }
}

public class CustomWebSocketManager
{
 private readonly RequestDelegate _next;

 public CustomWebSocketManager(RequestDelegate next)
 {
 _next = next;
 }

 public async Task Invoke(HttpContext context, ICustomWebSocketFactory wsFactory, ICustomWebSocketMessageHandler wsmHandler)
 {
 if (context.Request.Path == "/ws")
 {
 if (context.WebSockets.IsWebSocketRequest)
 {
 string username = context.Request.Query["u"];
 if (!string.IsNullOrEmpty(username))
 {
 WebSocket webSocket = await context.WebSockets.AcceptWebSocketAsync();
 CustomWebSocket userWebSocket = new CustomWebSocket()
 {
 WebSocket = webSocket,
 Username = username
 };
 wsFactory.Add(userWebSocket);
 await wsmHandler.SendInitialMessages(userWebSocket);
 await Listen(context, userWebSocket, wsFactory, wsmHandler);
 }
 }
 else
 {
 context.Response.StatusCode = 400;
 }
 }
 await _next(context);
 }

 private async Task Listen(HttpContext context, CustomWebSocket userWebSocket, ICustomWebSocketFactory wsFactory, ICustomWebSocketMessageHandler wsmHandler)
 {
 WebSocket webSocket = userWebSocket.WebSocket;
 var buffer = new byte[1024 * 4];
 WebSocketReceiveResult result = await webSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);
 while (!result.CloseStatus.HasValue)
 {
 await wsmHandler.HandleMessage(result, buffer, userWebSocket, wsFactory);
 buffer = new byte[1024 * 4];
 result = await webSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);
 } 
 wsFactory.Remove(userWebSocket.Username);
 await webSocket.CloseAsync(result.CloseStatus.Value, result.CloseStatusDescription, CancellationToken.None);
 }
}

在這種情況下，WebSockets請求在URL中始終包含“/ ws”。查詢字符串包含用于將WebSocket與登錄用戶相關聯的用戶名的參數u。

CustomWebSocket是一個包含WebSocket和用戶名的類：

public class CustomWebSocket
{
 public WebSocket WebSocket { get; set; }
 public string Username { get; set; }
}

我也創建了自定義WebSocket消息:

class CustomWebSocketMessage
{
 public string Text { get; set; }
 public DateTime MessagDateTime { get; set; }
 public string Username { get; set; }
 public WSMessageType Type { get; set; }
}

其中Type是您可能擁有的不同類型消息的枚舉。

在Startup類中，您必須注冊以下服務：

services.AddSingleton<ICustomWebSocketFactory, CustomWebSocketFactory>();
services.AddSingleton<ICustomWebSocketMessageHandler, CustomWebSocketMessageHandler>();

CustomWebSocketFactory負責收集連接的WebSockets列表：

public interface ICustomWebSocketFactory
{
 void Add(CustomWebSocket uws);
 void Remove(string username);
 List<CustomWebSocket> All();
 List<CustomWebSocket> Others(CustomWebSocket client);
 CustomWebSocket Client(string username);
}

public class CustomWebSocketFactory : ICustomWebSocketFactory
{
 List<CustomWebSocket> List;

 public CustomWebSocketFactory()
 {
 List = new List<CustomWebSocket>();
 }

 public void Add(CustomWebSocket uws)
 {
 List.Add(uws);
 }

 //when disconnect
 public void Remove(string username) 
 {
 List.Remove(Client(username));
 }

 public List<CustomWebSocket> All()
 {
 return List;
 }
 
 public List<CustomWebSocket> Others(CustomWebSocket client)
 {
 return List.Where(c => c.Username != client.Username).ToList();
 }
 
 public CustomWebSocket Client(string username)
 {
 return List.First(c=>c.Username == username);
 }
}

CustomWebSocketMessageHandler包含有關消息的邏輯（即在連接時需要發送任何消息以及如何對傳入消息作出反應）

public interface ICustomWebSocketMessageHandler
{
 Task SendInitialMessages(CustomWebSocket userWebSocket);
 Task HandleMessage(WebSocketReceiveResult result, byte[] buffer, CustomWebSocket userWebSocket, ICustomWebSocketFactory wsFactory);
 Task BroadcastOthers(byte[] buffer, CustomWebSocket userWebSocket, ICustomWebSocketFactory wsFactory);
 Task BroadcastAll(byte[] buffer, CustomWebSocket userWebSocket, ICustomWebSocketFactory wsFactory);
}

public class CustomWebSocketMessageHandler : ICustomWebSocketMessageHandler
{
 public async Task SendInitialMessages(CustomWebSocket userWebSocket)
 {
 WebSocket webSocket = userWebSocket.WebSocket;
 var msg = new CustomWebSocketMessage
 {
 MessagDateTime = DateTime.Now,
 Type = WSMessageType.anyType,
 Text = anyText,
 Username = "system"
 };

 string serialisedMessage = JsonConvert.SerializeObject(msg);
 byte[] bytes = Encoding.ASCII.GetBytes(serialisedMessage);
 await webSocket.SendAsync(new ArraySegment<byte>(bytes, 0, bytes.Length), WebSocketMessageType.Text, true, CancellationToken.None);
 }

 public async Task HandleMessage(WebSocketReceiveResult result, byte[] buffer, CustomWebSocket userWebSocket, ICustomWebSocketFactory wsFactory)
 {
 string msg = Encoding.ASCII.GetString(buffer);
 try
 {
 var message = JsonConvert.DeserializeObject<CustomWebSocketMessage>(msg);
 if (message.Type == WSMessageType.anyType)
 {
 await BroadcastOthers(buffer, userWebSocket, wsFactory);
 }
 }
 catch (Exception e)
 {
 await userWebSocket.WebSocket.SendAsync(new ArraySegment<byte>(buffer, 0, result.Count), result.MessageType, result.EndOfMessage, CancellationToken.None);
 }
 }

 public async Task BroadcastOthers(byte[] buffer, CustomWebSocket userWebSocket, ICustomWebSocketFactory wsFactory)
 {
 var others = wsFactory.Others(userWebSocket);
 foreach (var uws in others)
 {
 await uws.WebSocket.SendAsync(new ArraySegment<byte>(buffer, 0, buffer.Length), WebSocketMessageType.Text, true, CancellationToken.None);
 }
 }

 public async Task BroadcastAll(byte[] buffer, CustomWebSocket userWebSocket, ICustomWebSocketFactory wsFactory)
 {
 var all = wsFactory.All();
 foreach (var uws in all)
 {
 await uws.WebSocket.SendAsync(new ArraySegment<byte>(buffer, 0, buffer.Length), WebSocketMessageType.Text, true, CancellationToken.None);
 }
 }
}

最后，在Configure方法的Startup類中添加以下內容：

var webSocketOptions = new WebSocketOptions()
{
 KeepAliveInterval = TimeSpan.FromSeconds(120),
 ReceiveBufferSize = 4 * 1024
};

app.UseWebSockets(webSocketOptions);
app.UseCustomWebSocketManager();

通過這種方式，Starup類保持干凈，管理WebSockets的邏輯可以擴展，使您可以根據自己的喜好靈活地組織它。

總結

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