.NetCore WebSocket

我喜欢.NET CORE 这个东西，其实不仅仅源于它性能很高，可以跨平台，还因为它的设计模式确实令人着迷。以前没.NET CORE 的时候，.NET用websocket必须跑在windows server 2012上，但我一般不会这么干，都把websocket架在nodejs的服务器上。这么分出来，麻烦肯定是麻烦的，而且js这东西，写复杂和几年后再看都是头疼的问题。那么，如果.NET CORE是以kestrel运行的，那么就不再需要考虑服务器的版本运行，任何一个地方都可以用websocket

.net core使用websocket非常简单，中间件这个概念在.net core中是体现的淋漓尽致，而且不得不说真的是非常高明的一种设计模式。默认是不启用websocket的，那么我仅仅需要在Configure中app.UseWebSockets();来启用，再自己写一个中间件即可

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

namespace Common
{
    public static class MidWare
    {
        public static IApplicationBuilder UseWebSocket(this IApplicationBuilder builder)
        {
            return builder.UseMiddleware<SocketHelper.WebSocketMidWare>();
        }
    }
}

Configure中app.UseWebSocket();

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

namespace Common
{
    public class SocketHelper
    {
        public static async Task<string> RecvAsync(WebSocket webSocket, CancellationToken cancellationToken)
        {
            var ms = new MemoryStream();
            var buffer = new ArraySegment<byte>(new byte[1024 * 8]);

            WebSocketReceiveResult result;
            do
            {
                result = await webSocket.ReceiveAsync(buffer, cancellationToken);
                ms.Write(buffer.Array, buffer.Offset, result.Count - buffer.Offset);
            } while (!result.EndOfMessage);
            ms.Seek(0, SeekOrigin.Begin);
            var reader = new StreamReader(ms);
            var s = reader.ReadToEnd();
            reader.Dispose();
            ms.Dispose();
            return s;
        }


        public static async Task SendAsync(WebSocket webSocket,string msg )
        {
            CancellationToken cancellation=default(CancellationToken);
            var buf = Encoding.UTF8.GetBytes(msg);
            var segment = new ArraySegment<byte>(buf);
            await webSocket.SendAsync(segment, WebSocketMessageType.Text, true, cancellation);
        }
        public class WebSocketMidWare
        {
            private readonly RequestDelegate _next;
            public WebSocketMidWare(RequestDelegate next)
            {
                _next = next;
            }

            public async Task Invoke(HttpContext context)
            {
                if (context.Request.Path == "/ws" && context.WebSockets.IsWebSocketRequest)
                {
                    var socket = await context.WebSockets.AcceptWebSocketAsync();
                }
                else
                {
                    await _next(context);
                }
            }
        }

    }
}