c# 创建一个WebSocketServer 项目

可以按照以下步骤创建一个 C# WebSocketServer 项目：

1. 创建一个新的 C# 控制台应用程序项目。
2. 添加 `System.Net.WebSockets` 命名空间。
3. 在 `Program.cs` 文件中添加以下代码：

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

namespace WebSocketServer
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var listener = new HttpListener();
            listener.Prefixes.Add("http://localhost:8080/");
            listener.Start();

            Console.WriteLine("Listening...");

            while (true)
            {
                var context = await listener.GetContextAsync();
                if (context.Request.IsWebSocketRequest)
                {
                    ProcessWebSocketRequest(context);
                }
                else
                {
                    context.Response.StatusCode = 400;
                    context.Response.Close();
                }
            }
        }

        static async void ProcessWebSocketRequest(HttpListenerContext context)
        {
            try
            {
                var webSocket = await context.AcceptWebSocketAsync(subProtocol: null);
                Console.WriteLine("WebSocket connected");

                var buffer = new byte[1024 * 4];
                WebSocketReceiveResult result = null;

                while (webSocket.State == WebSocketState.Open)
                {
                    result = await webSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);

                    if (result.MessageType == WebSocketMessageType.Text)
                    {
                        var message = System.Text.Encoding.UTF8.GetString(buffer, 0, result.Count);
                        Console.WriteLine($"Received message: {message}");

                        var responseBytes = System.Text.Encoding.UTF8.GetBytes($"Echo: {message}");
                        await webSocket.SendAsync(new ArraySegment<byte>(responseBytes), WebSocketMessageType.Text, true, CancellationToken.None);
                    }
                    else if (result.MessageType == WebSocketMessageType.Close)
                    {
                        await webSocket.CloseAsync(result.CloseStatus.Value, result.CloseStatusDescription, CancellationToken.None);
                        Console.WriteLine("WebSocket closed");
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"WebSocket error: {ex.Message}");
            }
        }
    }
}

4. 运行程序，WebSocket 服务器将在 `http://localhost:8080/` 上监听连接请求。当客户端连接时，服务器将打印一条消息并开始接收客户端发送的消息。当接收到消息时，服务器将打印消息内容并将其回显给客户端。客户端可以通过发送 `Close` 消息来关闭 WebSocket 连接。