C# WebSocket服务端 代码

在C#中，WebSocket服务端通常使用`System.Net.WebSockets命名空间`提供的类来实现。下面是一个简单的例子，展示了一个基础的WebSocket服务器：

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Server.Kestrel.Core;

public class WebSocketServer
{
    private readonly List<string> _clients = new List<string>();

    public void Start()
    {
        var serverBuilder = WebHost.CreateDefaultBuilder()
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseKestrel(options =>
                {
                    options.Listen(5000, "localhost");
                })
                .UseStartup<Startup>();
            });

        using (var server = serverBuilder.Build())
        {
            server.Run();
        }
    }

    public class Startup
    {
        // Configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();

            app.UseWebSockets((context) =>
            {
                context.WebSocket.OnOpen(async (sender, e) =>
                {
                    _clients.Add(context.WebSocket.RemoteAddress.ToString());
                    await context.SendAsync($"Welcome! You are connected with ID {_clients.Count - 1}", WebSocketMessageType.Text, true);
                });

                context.WebSocket.OnClose(async (sender, e) =>
                {
                    _clients.Remove(context.WebSocket.RemoteAddress.ToString());
                    await context.SendAsync($"Goodbye! User {e.CloseStatus} has disconnected", WebSocketMessageType.Text, true);
                });

                context.WebSocket.OnMessageAsync(async (sender, e) =>
                {
                    foreach (var client in _clients)
                    {
                        await context.WebSocket.SendAsync(e.Data, WebSocketMessageType.Text, true, endOfMessage: false);
                    }
                });
            });
        }
    }
}

这个示例创建了一个WebSocket服务器监听本地的5000端口，当新的客户端连接时，它会发送欢迎信息，并处理消息广播。当用户断开连接时，会发送告别信息。