Asp.net webApi 通过WebSocket推送消息给客户端，搭建一个即是服务端又是客户端的服务

https://blog.csdn.net/IT_ziliang/article/details/96478794

WebSocket是一种在单个TCP连接上进行全双工通信的协议。WebSocket通信协议于2011年被IETF定为标准RFC 6455，并由RFC7936补充规范。WebSocket API也被W3C定为标准。

WebSocket使得客户端和服务器之间的数据交换变得更加简单，允许服务端主动向客户端推送数据。在WebSocket API中，浏览器和服务器只需要完成一次握手，两者之间就直接可以创建持久性的连接，并进行双向数据传输。

废话不多说了，直接手把手教你如何通信

1、首先新建一个UserController继承自ApiController，然后写一个get方法供外部去调用。方法上一定加上 [HttpGet]，代码如下

[HttpGet]
        public HttpResponseMessage GetConnect(string clientName)
        {
            HttpContext.Current.AcceptWebSocketRequest(ProcessRequest); //在服务器端接受Web Socket请求，传入的函数作为Web Socket的处理函数，待Web Socket建立后该函数会被调用，在该函数中可以对Web Socket进行消息收发
 
            return Request.CreateResponse(HttpStatusCode.SwitchingProtocols); //构造同意切换至Web Socket的Response.
        }
        ///记录客户端
        private static List<WebSocket> _sockets = new List<WebSocket>();
        ///接受信息和发送信息
        public async Task ProcessRequest(AspNetWebSocketContext context)
        {
            try
            {
                var socket = context.WebSocket;//传入的context中有当前的web socket对象
                _sockets.Add(socket);//此处将web socket对象加入一个静态列表中
 
                //进入一个无限循环，当web socket close是循环结束
                while (true)
                {
                    var buffer = new ArraySegment<byte>(new byte[1024]);
                    var receivedResult = await socket.ReceiveAsync(buffer, CancellationToken.None);//对web socket进行异步接收数据
                    if (receivedResult.MessageType == WebSocketMessageType.Close)
                    {
                        await socket.CloseAsync(WebSocketCloseStatus.Empty, string.Empty, CancellationToken.None);//如果client发起close请求，对client进行ack
                        _sockets.Remove(socket);
                        break;
                    }
 
                    if (socket.State == System.Net.WebSockets.WebSocketState.Open)
                    {
                        string recvMsg = Encoding.UTF8.GetString(buffer.Array, 0, receivedResult.Count);
                        var recvBytes = Encoding.UTF8.GetBytes(recvMsg);
                        var sendBuffer = new ArraySegment<byte>(recvBytes);
                        foreach (var innerSocket in _sockets)//当接收到文本消息时，对当前服务器上所有web socket连接进行广播
                        {
                            if (innerSocket != socket)
                            {
                                await innerSocket.SendAsync(sendBuffer, WebSocketMessageType.Text, true, CancellationToken.None);
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                logger.Error(ex.Message);//lognet4日志记录
            }
        }
    }

2、如何做一个有信息就发送给所有客户端尼？就是再写个方法当作客户端发送信息给服务端就可以了，不用服务端去时时轮询。代码如下这个方法就写在同一个类中，直接调用就行

        private readonly ClientWebSocket webSocket = new ClientWebSocket();
        private readonly CancellationToken _cancellation = new CancellationToken();
        ///客户端发送消息
        private async void SendMsg(object data)
        {
            try
            {
                await webSocket.ConnectAsync(new Uri("ws://localhost:8080/api/User?clientName=" + 123), _cancellation);
                var sendBytes = ObjectToBytes(data);//发送的数据
                var bsend = new ArraySegment<byte>(sendBytes);
                await webSocket.SendAsync(bsend, WebSocketMessageType.Binary, true, _cancellation);
                await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "1", _cancellation);
                webSocket.Dispose();//记得一定要释放不然服务端还产生很多连接
            }
            catch (Exception ex)
            {
                logger.Error(ex.Message);//lognet4日志记录
            }
        }

3、网页版的客户端代码如下

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
 <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0"/>
 <title></title>
<script src="https://ajax.aspnetcdn.com/ajax/jquery/jquery-1.11.3.min.js"></script>
 <script>
 var ws;
 $().ready(function () {
  $('#conn').click(function () {
  ws = new WebSocket('ws://localhost:8080' + '/api/user?clientName='+'456');
  $('#msg').append('<p>正在连接</p>');
 
  ws.onopen = function () {
   $('#msg').append('<p>已经连接</p>');
  }
  ws.onmessage = function (evt) {
   $('#msg').append('<p>' + evt.data + '</p>');
  }
  ws.onerror = function (evt) {
   $('#msg').append('<p>' + JSON.stringify(evt) + '</p>');
  }
  ws.onclose = function () {
   $('#msg').append('<p>已经关闭</p>');
  }
  });
 
  $('#close').click(function () {
  ws.close();
  });
 
  $('#send').click(function () {
  if (ws.readyState == WebSocket.OPEN) {
   ws.send($("#to").val() + "|" + $('#content').val());
  }
  else {
   $('#tips').text('连接已经关闭');
  }
  });
 
 });
 </script>
</head>
<body>
 <div>
 <input id="user" type="text" />
 <input id="conn" type="button" value="连接" />
 <input id="close" type="button" value="关闭"/><br />
 <span id="tips"></span>
 <input id="content" type="text" />
 <input id="send" type="button" value="发送"/><br />
 <input id="to" type="text" />目的用户
 <div id="msg">
 </div>
 </div>
</body>
</html>

4、C#控制台客户端的代码如下

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.WebSockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
 
namespace WebSocketClient
{
    class Program
    {
        static ClientWebSocket _webSocket = new ClientWebSocket();
        static CancellationToken _cancellation = new CancellationToken();
        static void Main(string[] args)
        {
            WebSocket();
            Console.Read();
        }
 
        public static async void WebSocket()
        {
            try
            {
 
                //建立连接
                var url = "ws://localhost:8080/api/User?clientName=" + 456;
 
                await _webSocket.ConnectAsync(new Uri(url), _cancellation);
                while (true)
                {
                    var result = new byte[1024];
                    await _webSocket.ReceiveAsync(new ArraySegment<byte>(result), new CancellationToken());//接受数据
                    var str = Encoding.UTF8.GetString(result, 0, result.Length);
                    Console.WriteLine(str);//打印到控制台
                }
 
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }
    }
}

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