Asp.net Core中如何使用中间件来管理websocket
介绍
我喜欢.NET CORE 这个东西，其实不仅仅源于它性能很高，可以跨平台，还因为它的设计模式确实令人着迷。以前没.NET CORE 的时候，.NET用websocket必须跑在windows server 2012上，但我一般不会这么干，都把websocket架在nodejs的服务器上。这么分出来，麻烦肯定是麻烦的，而且js这东西，写复杂和几年后再看都是头疼的问题。那么，如果.NET CORE是以kestrel运行的，那么就不再需要考虑服务器的版本运行，任何一个地方都可以用websocket
ASP.NET Core SignalR是一个有用的库，可以简化Web应用程序中实时通信的管理。但是，我宁愿使用WebSockets，因为我想要更灵活，并且与任何WebSocket客户端兼容。
在Microsoft的文档中，我找到了一个很好的WebSockets工作示例。它仍然是管理连接，以便能够从一个连接向其他连接广播消息，这是SignalR开箱即用的功能。期望这个逻辑非常复杂，我想从Startup类中删除它。
背景
要阅读ASP.NET Core中的WebSockets支持，可以在此处查看。如果您想了解中间件以及如何在ASP.NET Core中编写它，请阅读此链接。
代码使用
首先，你必须添加 Microsoft.AspNetCore.WebSockets 包到你的项目。
现在，您可以创建一个扩展方法和类来管理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);
}
}
在这种情况下，WebSockets请求在URL中始终包含“/ ws”。查询字符串包含用于将WebSocket与登录用户相关联的用户名的参数u。
CustomWebSocket是一个包含WebSocket和用户名的类：
public class CustomWebSocket
{
public WebSocket WebSocket { get; set; }
public string Username { get; set; }
}
我也创建了自定义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是您可能拥有的不同类型消息的枚举。
在Startup类中，您必须注册以下服务：
services.AddSingleton<ICustomWebSocketFactory, CustomWebSocketFactory>();
services.AddSingleton<ICustomWebSocketMessageHandler, CustomWebSocketMessageHandler>();
CustomWebSocketFactory负责收集连接的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包含有关消息的逻辑（即在连接时需要发送任何消息以及如何对传入消息作出反应）
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类中添加以下内容：
var webSocketOptions = new WebSocketOptions()
{
KeepAliveInterval = TimeSpan.FromSeconds(120),
ReceiveBufferSize = 4 * 1024
};
app.UseWebSockets(webSocketOptions);
app.UseCustomWebSocketManager();
通过这种方式，Starup类保持干净，管理WebSockets的逻辑可以扩展，使您可以根据自己的喜好灵活地组织它。
总结
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