WebSocket In ASP.NET Core(二)

Introduce

上篇博文中，介绍了WebSocket的基本原理，以及一个简单的Demo用来对其有一个大致的认识。这篇博文讲的是我们平常在网站上可能会经常遇到的——实时聊天，本文就是来讲在.NET-Core使用WebSocket来实现一个“乞丐版”的在线实时聊天Demo。

关键词：Middleware,Real-Time,WebSocket

Before You Read.

这个和我们上一篇博文中Demo 有何不同的呢？有何共同之处呢？

相同的点是，都是网页作为客户端，使用JavaScript来发送和接收请求，.NET-Core 服务端接收到请求，发送该请求给客户端。

不同的地方呢，就像我下面这张图这样：

一次同时有多个客户端在，所以应该很清楚，我们只要在上面例子的基础上，对当前的已存在的Socket进行轮询，发送回应即可达到我们想要的效果。

Create WebSocket Middleware

在上个Demo的例子中，我们直接在Startup 的Configure 中直接写接受WebSocket请求。这次我们换成Middleware形式来处理。在写Middleware之前，在之前的介绍中，我们知道，需要有多个WebSocket，那么肯定需要一些对WebSocket 的Get/Set 处理。我简单的写了一个下面WebScoket Manger Class

//WebSocketManager.csusing System;using System.Collections.Concurrent;using System.Collections.Generic;using System.Linq;using System.Net.WebSockets;using System.Text;using System.Threading;using System.Threading.Tasks;

namespace WebSocketManage{    public class WSConnectionManager    {        private static ConcurrentDictionary<string, WebSocket> _socketConcurrentDictionary = new ConcurrentDictionary<string, WebSocket>();

        public void AddSocket(WebSocket socket)        {            _socketConcurrentDictionary.TryAdd(CreateGuid(), socket);        }

        public async Task RemoveSocket(WebSocket socket)        {            _socketConcurrentDictionary.TryRemove(GetSocketId(socket), out WebSocket aSocket);

            await aSocket.CloseAsync(                closeStatus: WebSocketCloseStatus.NormalClosure,                statusDescription: "Close by User",                cancellationToken: CancellationToken.None).ConfigureAwait(false);        }

        public string GetSocketId(WebSocket socket)        {            return _socketConcurrentDictionary.FirstOrDefault(k => k.Value == socket).Key;        }

        public ConcurrentDictionary<string, WebSocket> GetAll()        {            return _socketConcurrentDictionary;        }

        public string CreateGuid()        {            return Guid.NewGuid().ToString();        }    }}

上面主要是对WebSocket 进行了简单的存取操作进行了封装。下面也把WebSocket 的Send 和Recieve 操作进行了封装。

using System;using System.Collections.Generic;using System.IO;using System.Net.WebSockets;using System.Text;using System.Threading;using System.Threading.Tasks;

namespace WebSocketManage{    public class WSHandler    {        protected WSConnectionManager _wsConnectionManager;

        public WSHandler(WSConnectionManager wSConnectionManager)        {            _wsConnectionManager = wSConnectionManager;        }

        public async Task SendMessageAsync(            WebSocket socket,            string message,            CancellationToken cancellationToken = default(CancellationToken))        {            var buffer = Encoding.UTF8.GetBytes(message);            var segment = new ArraySegment<byte>(buffer);

            await socket.SendAsync(segment, WebSocketMessageType.Text, true, cancellationToken);        }        public async Task<string> RecieveAsync(WebSocket webSocket, CancellationToken cancellationToken)        {            var buffer = new ArraySegment<byte>(new byte[1024 * 8]);            using (var ms = new MemoryStream())            {                WebSocketReceiveResult result;                do                {                    cancellationToken.ThrowIfCancellationRequested();

                    result = await webSocket.ReceiveAsync(buffer, cancellationToken);                    ms.Write(buffer.Array, buffer.Offset, result.Count);                }                while (!result.EndOfMessage);

                ms.Seek(0, SeekOrigin.Begin);                if (result.MessageType != WebSocketMessageType.Text)                {                    return null;                }

                using (var reader = new StreamReader(ms, Encoding.UTF8))                {                    return await reader.ReadToEndAsync();                }            }        }    }}有了上面两个辅助类之后，接下来就可以写我们自己的RealTimeWebSocketMiddlerware 了，

using Microsoft.AspNetCore.Http;using System;using System.Collections.Generic;using System.IO;using System.Net.WebSockets;using System.Text;using System.Threading;using System.Threading.Tasks;using WebSocketManage;

namespace Robert.Middleware.WebSockets{    public class RealTimeWSMiddleware    {        private readonly RequestDelegate _next;        private WSConnectionManager _wSConnectionManager { get; set; }        private WSHandler _wsHanlder { get; set; }

        public RealTimeWSMiddleware(            RequestDelegate next,            WSConnectionManager wSConnectionManager,            WSHandler wsHandler)        {            _next = next;            _wSConnectionManager = wSConnectionManager;            _wsHanlder = wsHandler;        }

        public async Task Invoke(HttpContext httpContext)        {            if (httpContext.WebSockets.IsWebSocketRequest)            {                var cancellationToken = httpContext.RequestAborted;                var currentWebSocket = await httpContext.WebSockets.AcceptWebSocketAsync();                _wSConnectionManager.AddSocket(currentWebSocket);

                while (true)                {                    if (cancellationToken.IsCancellationRequested) break;                    var response = await _wsHanlder.ReceiveAsync(currentWebSocket, cancellationToken);

                    if (string.IsNullOrEmpty(response) && currentWebSocket.State != WebSocketState.Open) break;

                    foreach (var item in _wSConnectionManager.GetAll())                    {                        if (item.Value.State == WebSocketState.Open)                        {                            await _wsHanlder.SendMessageAsync(item.Value, response, cancellationToken);                        }                        continue;                    }                }

                await _wSConnectionManager.RemoveSocket(currentWebSocket);            }            else            {                await _next(httpContext);            }        }    }}

有了上面两个辅助类之后，接下来就可以写我们自己的RealTimeWebSocketMiddlerware 了，

using Microsoft.AspNetCore.Http;

using System;

using System.Collections.Generic;

using System.IO;

using System.Net.WebSockets;

using System.Text;

using System.Threading;

using System.Threading.Tasks;

using WebSocketManage;

namespace Robert.Middleware.WebSockets

{

public class RealTimeWSMiddleware

{

private readonly RequestDelegate _next;

private WSConnectionManager _wSConnectionManager { get; set; }

private WSHandler _wsHanlder { get; set; }

public RealTimeWSMiddleware(

RequestDelegate next,

WSConnectionManager wSConnectionManager,

WSHandler wsHandler)

{

_next = next;

_wSConnectionManager = wSConnectionManager;

_wsHanlder = wsHandler;

}

public async Task Invoke(HttpContext httpContext)

{

if (httpContext.WebSockets.IsWebSocketRequest)

{

var cancellationToken = httpContext.RequestAborted;

var currentWebSocket = await httpContext.WebSockets.AcceptWebSocketAsync();

_wSConnectionManager.AddSocket(currentWebSocket);

while (true)

{

if (cancellationToken.IsCancellationRequested) break;

var response = await _wsHanlder.ReceiveAsync(currentWebSocket, cancellationToken);

if (string.IsNullOrEmpty(response) && currentWebSocket.State != WebSocketState.Open) break;

foreach (var item in _wSConnectionManager.GetAll())

{

if (item.Value.State == WebSocketState.Open)

{

await _wsHanlder.SendMessageAsync(item.Value, response, cancellationToken);

}

continue;

}

await _wSConnectionManager.RemoveSocket(currentWebSocket);

}

else

{

await _next(httpContext);

}

其实到这里，核心部分已经讲完了，接下来就是页面显示，发现信息，交互的问题了。在客户端还是像上篇文章中的一样，直接使用 JavaScript发送WebScoket请求。

下面主要演示一下效果，在上篇博文的基础上，加上了用户名。

<script>$(function () {var protocol = location.protocol === "https:" ? "wss:" : "ws:";var Uri = protocol + "//" + window.location.host + "/ws";var socket = new WebSocket(Uri);socket.onopen = e => {console.log("socket opened", e);};socket.onclose = function (e) {console.log("socket closed", e);};//function to receive from server.socket.onmessage = function (e) {console.log("Message:" + e.data);$('#msgs').append(e.data + '<br />');};socket.onerror = function (e) {console.error(e.data);};});</script>

当写好了页面文件后，运行站点。最终运行的效果图，界面以实用为主，不求美观。