c#开发 websocketserver 给指定客服端发信息

在 C# 中，你可以使用 System.Net.WebSockets API 来创建一个 WebSocket 服务器，允许向特定客户端发送消息。以下是一个简单的步骤概述：

1. 引入必要的库：

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.WebSockets;

2. 创建WebSocket中间件：

public static IApplicationBuilder UseWebSockets(this IApplicationBuilder builder)
{
    return builder.UseMiddleware<WebSocketServerMiddleware>();
}

3. 定义 `WebSocketServerMiddleware` 类：

public class WebSocketServerMiddleware
{
    private readonly RequestDelegate _next;

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

    public async Task InvokeAsync(HttpContext context)
    {
        if (context.WebSockets.IsWebSocketRequest)
        {
            var socket = await context.WebSockets.AcceptWebSocketAsync();
            var clients = new Dictionary<string, WebSocket>();

            // 添加新连接到字典
            clients.Add(socket.ConnectionId, socket);

            try
            {
                while (true)
                {
                    var message = await socket.ReceiveMessageAsync();

                    // 根据需求判断是否给指定客户端发送信息
                    if (IsTargetClient(clients, "your-target-client-id")) // 替换为实际的客户端ID
                    {
                        await SendToSpecificClient(socket, message);
                    }
                }
            }
            catch (WebSocketCloseStatus wsCloseStatus)
            {
                Console.WriteLine($"Connection closed by client: {wsCloseStatus}");
            }
            finally
            {
                // 断开连接时从字典中移除
                clients.Remove(socket.ConnectionId);
            }
        }
        else
        {
            await _next(context);
        }
    }

    private bool IsTargetClient(Dictionary<string, WebSocket> clients, string targetClientId)
    {
        return clients.ContainsKey(targetClientId);
    }

    private async Task SendToSpecificClient(WebSocket socket, Message receivedMessage)
    {
        // 构建并发送回特定客户端的消息
        var messageBytes = Encoding.UTF8.GetBytes("Your message here");
        await socket.SendAsync(new ArraySegment<byte>(messageBytes), WebSocketMessageType.Text, true);
    }
}

4. 在启动应用程序时启用WebSocket服务：

app.UseWebSockets();

在这个例子中，你需要有一个标识目标客户端的方法（如 `IsTargetClient`），以及一个将消息发送到指定客户端的方法（如 `SendToSpecificClient`）。你需要替换掉“your-target-client-id”和“Your message here”以适应你的实际需求。