一、SignalR是什么
Asp.net SignalR是微软为实现实时通信的一个类库。一般情况下，SignalR会使用JavaScript的长轮询(long polling)的方式来实现客户端和服务器通信，随着Html5中WebSockets出现，SignalR也支持WebSockets通信。另外SignalR开发的程序不仅仅限制于宿主在IIS中，也可以宿主在任何应用程序，包括控制台，客户端程序和Windows服务等，另外还支持Mono，这意味着它可以实现跨平台部署在Linux环境下。
SignalR内部有两类对象：
Http持久连接(Persisten Connection)对象：用来解决长时间连接的功能。还可以由客户端主动向服务器要求数据，而服务器端不需要实现太多细节，只需要处理PersistentConnection 内所提供的五个事件：OnConnected, OnReconnected, OnReceived, OnError 和 OnDisconnect 即可。
Hub（集线器）对象：用来解决实时(realtime)信息交换的功能，服务端可以利用URL来注册一个或多个Hub，只要连接到这个Hub，就能与所有的客户端共享发送到服务器上的信息，同时服务端可以调用客户端的脚本。
SignalR将整个信息的交换封装起来，客户端和服务器都是使用JSON来沟通的，在服务端声明的所有Hub信息，都会生成JavaScript输出到客户端，.NET则依赖Proxy来生成代理对象，而Proxy的内部则是将JSON转换成对象。
二、为什么要用SignalR
聊天室，如在线客服系统，IM系统等
消息的实时推送服务
巡更人员位置的实时推送
1. server -------- 创建一个MVC 项目,选择新建的项目，右击-->选择管理NuGet程序包-->搜索 signalr--> 安装Microsoft ASP.NET SignalR
新建启动程序 Startup.cs
在类中添加代码：
- app.MapSignalR();
在集线器类ChatHub.cs中添加如下代码
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using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Web;
using Microsoft.AspNet.SignalR;
using System.Threading.Tasks;
namespace ChatServer
{
public class ChatHub : Hub
{
public void Hello()
{
//Clients.All.hello();
//Clients.All.AddMsg();
}
/// <summary>
/// 供客户端调用的服务器端代码
/// </summary>
/// <param name="message"></param>
public void Send(string name,string message)
{
// 调用所有客户端的sendMessage方法
Clients.All.sendMessage(name, message);
Trace.WriteLine("调用所有客户端的sendMessage方法");
}
/// <summary>
/// 客户端连接的时候调用
/// </summary>
/// <returns></returns>
public override Task OnConnected()
{
Trace.WriteLine("客户端连接成功");
return base.OnConnected();
}
}
}
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2. 客户端（winform）
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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Microsoft.AspNet.SignalR.Client;
namespace ChatClient
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
Text = "Test SignalR";
FormClosing += Form1_FormClosing;
}
public IHubProxy HubProxy { get; set; }
const string ServerURI = "https://localhost:44306/";//ServerURI = "https://localhost:44306/signalr";
public HubConnection Connection { get; set; }
/// <summary>
/// Creates and connects the hub connection and hub proxy. This method
/// is called asynchronously
/// </summary>
private async void ConnectAsync()
{
Connection = new HubConnection(ServerURI);
Connection.Closed += ShowConnectionClosed;
HubProxy = Connection.CreateHubProxy("ChatHub");
//Handle incoming event from server: use Invoke to write to console from SignalR's thread
HubProxy.On<string, string>("sendMessage", (name, message) =>
{
this.Invoke(
new Action(() =>
{
RichTextBoxConsole.AppendText(String.Format("{0}: {1}\r", name, message));
}
));
}
);
try
{
await Connection.Start();
}
catch (HttpRequestException)
{
Text = "Unable to connect to server: Start server before connecting clients.";
//No connection: Don't enable Send button or show chat UI
return;
}
TextBoxMessage.Focus();
RichTextBoxConsole.AppendText("Connected to server at " + ServerURI + "\r");
}
private void CloseConnection()
{
if (Connection != null)
{
Connection.Stop();
Connection.Dispose();
}
}
/// <summary>
/// If the server is stopped, the connection will time out after 30 seconds (default), and the
/// Closed event will fire.
/// </summary>
private void ShowConnectionClosed()
{
RichTextBoxConsole.AppendText("You have been disconnected.\r\n");
}
private void btnConnect_Click(object sender, EventArgs e)
{
RichTextBoxConsole.AppendText("Connecting to server...");
ConnectAsync();
}
private void btnSend_Click(object sender, EventArgs e)
{
if (Connection.State == Microsoft.AspNet.SignalR.Client.ConnectionState.Disconnected)
{
ShowConnectionClosed();
return;
}
HubProxy.Invoke("Send", "Client wgscd", TextBoxMessage.Text);
TextBoxMessage.Text = String.Empty;
TextBoxMessage.Focus();
}
private void btnDisconnect_Click(object sender, EventArgs e)
{
CloseConnection();
}
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
CloseConnection();
}
}
}
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