当前有一个需求，需要网页端调用扫描仪，javascript不具备调用能力，因此需要在机器上提供一个ws服务给前端网页调用扫描仪。而扫描仪有一个c#版本的API，因此需要寻找一个c#的websocket库。

java里有大名鼎鼎的netty，通过搜索，c#可以选择websocket-sharp来实现websocket Server。

使用websocket-sharp创建websocket server

using System;
using WebSocketSharp;
using WebSocketSharp.Server;namespace Example { public class Laputa : WebSocketBehavior { protected override void OnMessage (MessageEventArgs e) { var msg = e.Data == "BALUS" ? "I've been balused already..." : "I'm not available now."; Send (msg); } } public class Program { public static void Main (string[] args) { var wssv = new WebSocketServer ("ws://dragonsnest.far"); wssv.AddWebSocketService<Laputa> ("/Laputa"); wssv.Start (); Console.ReadKey (true); wssv.Stop (); } } }

Step 1

Required namespace.

using WebSocketSharp.Server;

The WebSocketBehavior and WebSocketServer 两个类需要引用 WebSocketSharp.Server namespace.

Step 2

编写处理类，需要继承 WebSocketBehavior class.

例如，如果你要创建一个echo Service,

using System;
using WebSocketSharp;
using WebSocketSharp.Server;public class Echo : WebSocketBehavior { protected override void OnMessage (MessageEventArgs e) { Send (e.Data); } }

再提供一个 chat service,

using System;
using WebSocketSharp;
using WebSocketSharp.Server;public class Chat : WebSocketBehavior { private string _suffix; public Chat () : this (null) { } public Chat (string suffix) { _suffix = suffix ?? String.Empty; } protected override void OnMessage (MessageEventArgs e) { Sessions.Broadcast (e.Data + _suffix); } }

可以通过继承WebSocketBehavior类来自定义Service.

通过重载 WebSocketBehavior.OnMessage (MessageEventArgs) 方法, 来处理消息

同时你也可以重载 WebSocketBehavior.OnOpen (), WebSocketBehavior.OnError (ErrorEventArgs), 和 WebSocketBehavior.OnClose (CloseEventArgs) 方法,来处理websocket连接事件。

通过WebSocketBehavior.Send 方法来给客户端发送消息。

If you would like to get the sessions in the service, you should access the WebSocketBehavior.Sessions property (returns a WebSocketSharp.Server.WebSocketSessionManager).

The WebSocketBehavior.Sessions.Broadcast method can send data to every client in the service.

Step 3

创建 WebSocketServer 对象.

var wssv = new WebSocketServer (4649);
wssv.AddWebSocketService<Echo> ("/Echo"); wssv.AddWebSocketService<Chat> ("/Chat"); wssv.AddWebSocketService<Chat> ("/ChatWithNyan", () => new Chat (" Nyan!"));

Step 4

启动 WebSocket server.

wssv.Start ();

Step 5

停止 WebSocket server.

wssv.Stop (code, reason);

测试Demo

目的：对外提供一个websocket服务，让网页端的js可以调用扫描仪

服务端代码

 class Program{static void Main(string[] args) { var wssv = new WebSocketServer(10086); wssv.AddWebSocketService<ScannerHandler>("/scan"); wssv.Start(); if (wssv.IsListening) { Console.WriteLine("Listening on port {0}, and providing WebSocket services:", wssv.Port); foreach (var path in wssv.WebSocketServices.Paths) Console.WriteLine("- {0}", path); } Console.WriteLine("\nPress Enter key to stop the server..."); Console.ReadLine(); wssv.Stop(); } } public class ScannerHandler : WebSocketBehavior { protected override void OnMessage(MessageEventArgs e) { if(e.Data == "scan") { ScanResult result = ScanerHelper.Scan("D:\\test.jpg"); if (result.Success) { Console.WriteLine("scan success"); Send("scan success"); } else { Send("scan eror"); } } } }

前端代码

javascript代码

    var ws;function initWS() { ws = new WebSocket("ws://127.0.0.1:10086/scan"); ws.onopen = function () { console.log("Openened connection to websocket"); }; ws.onclose = function () { console.log("Close connection to websocket"); // 断线重连 initWS(); } ws.onmessage = function (e) { alert(e.data) } } initWS(); function scan() { ws && ws.send('scan'); }

html代码

<button onclick="scan()">扫描</button>

• initWS创建连接，支持断线重连
• 可以调用scan函数，发送scan指令