.NET实现WebSocket服务端即时通信实例

好的，以下是一个简单的.NET WebSocket服务端即时通信实例，供您参考：

1. 首先，创建一个空的ASP.NET Web应用程序。

2. 在项目中添加一个类文件，命名为WebSocketHandler.cs，并在其中添加以下代码：

using System;
using System.Collections.Concurrent;
using System.Net.WebSockets;
using System.Threading;
using System.Threading.Tasks;

namespace WebSocketServer
{
    public class WebSocketHandler
    {
        private static ConcurrentDictionary<string, WebSocket> _sockets = new ConcurrentDictionary<string, WebSocket>();

        public async Task Handle(WebSocket socket)
        {
            var socketId = Guid.NewGuid().ToString();
            _sockets.TryAdd(socketId, socket);

            while (socket.State == WebSocketState.Open)
            {
                var buffer = new ArraySegment<byte>(new byte[4096]);
                WebSocketReceiveResult result = await socket.ReceiveAsync(buffer, CancellationToken.None);

                if (result.MessageType == WebSocketMessageType.Text)
                {
                    var message = System.Text.Encoding.UTF8.GetString(buffer.Array, buffer.Offset, result.Count);
                    await SendMessageToAllAsync(message);
                }
                else if (result.MessageType == WebSocketMessageType.Close)
                {
                    WebSocket removedSocket;
                    _sockets.TryRemove(socketId, out removedSocket);
                    await removedSocket.CloseAsync(result.CloseStatus.Value, result.CloseStatusDescription, CancellationToken.None);
                }
            }
        }

        private static async Task SendMessageToAllAsync(string message)
        {
            foreach (var socket in _sockets)
            {
                if (socket.Value.State == WebSocketState.Open)
                {
                    var buffer = new ArraySegment<byte>(System.Text.Encoding.UTF8.GetBytes(message));
                    await socket.Value.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None);
                }
            }
        }
    }
}

3. 在项目中添加一个WebSocketMiddleware.cs类文件，并在其中添加以下代码：

using System;
using System.Net.WebSockets;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;

namespace WebSocketServer
{
    public class WebSocketMiddleware
    {
        private readonly RequestDelegate _next;
        private WebSocketHandler _webSocketHandler { get; set; }

        public WebSocketMiddleware(RequestDelegate next, WebSocketHandler webSocketHandler)
        {
            _next = next;
            _webSocketHandler = webSocketHandler;
        }

        public async Task InvokeAsync(HttpContext context)
        {
            if (!context.WebSockets.IsWebSocketRequest)
            {
                await _next(context);
                return;
            }

            var socket = await context.WebSockets.AcceptWebSocketAsync();
            await _webSocketHandler.Handle(socket);
        }
    }
}

4. 在Startup.cs文件中添加以下代码：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;

namespace WebSocketServer
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddWebSocketManager();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.UseWebSockets();
            app.MapWebSocketManager("/ws", app.ApplicationServices.GetService<WebSocketHandler>());

            app.Run(async (context) =>
            {
                await context.Response.WriteAsync("Hello World!");
            });
        }
    }
}

5. 在项目中添加一个WebSocketExtensions.cs文件，并在其中添加以下代码：

using Microsoft.AspNetCore.Builder;

namespace WebSocketServer
{
    public static class WebSocketExtensions
    {
        public static IApplicationBuilder MapWebSocketManager(this IApplicationBuilder app, string path, WebSocketHandler handler)
        {
            return app.Map(path, (x) => x.UseMiddleware<WebSocketMiddleware>(handler));
        }
    }
}

6. 在项目中添加一个WebSocketManagerExtensions.cs文件，并在其中添加以下代码：

using Microsoft.Extensions.DependencyInjection;

namespace WebSocketServer
{
    public static class WebSocketManagerExtensions
    {
        public static IServiceCollection AddWebSocketManager(this IServiceCollection services)
        {
            services.AddSingleton<WebSocketHandler>();
            return services;
        }
    }
}

7. 运行应用程序，并使用WebSocket客户端连接到ws://localhost:5000/ws。您可以使用任何WebSocket客户端，如Chrome的WebSocket插件。

8. 您现在可以向服务器发送消息，并通过服务器将它们广播到所有连接的客户端。

希望这个例子能帮助到你！