目录
介绍
本技巧内容涵盖了在Web应用程序环境中使用SignalR进行实时通信的介绍性信息，其中服务器可以在客户端可用时立即将信息推送给客户端，而不是等待客户端从服务器请求数据。
SignalR对于万维网上的聊天应用程序，仪表板或游戏非常有用，但对于工业桌面应用程序也很重要。
如果您使用AJAX来提高Web应用程序的响应速度，那么SignalR是一个有用的替代方案。
您可以通过启用日志记录来确定SignalR正在使用的传输类型：
$.connection.hub.logging = true;如果您随后在Web浏览器上打开调试工具，您将看到诸如“SignalR：Websocket opened”之类的行。
什么是SignalR？
通常，要从服务器获取更多客户端上的数据（如果已更改），则必须使用HTTP执行轮询GET，这是AJAX所做的。如果你想要任何接近实时的东西，那么你必须经常进行轮询。相反，使用SignalR，您有一个持久连接，客户端可以调用服务器，服务器可以调用客户端。
因此，SignalR是一个开发人员库，它简化了实时通信，其中服务器和客户端连接是持久的，与传统的HTTP范例不同。
如果您的计算机使用的是Windows 8或Windows Server 2012或更高版本，以及.NET Framework 4.5，那么SignalR将使用WebSocket；否则，它将使用HTML 5传输或Comet传输。
连接和集线器(Hubs)
客户端和服务器之间通信的两种模型是持久连接和集线器。
连接表示发送单一收件人、分组或广播邮件的端点。
Hub是持久连接(Persistent Connections)之上的一个层，允许您的客户端和服务器直接相互调用方法。使用.NET Remoting的.NET开发人员会熟悉此模型。这允许您传递强类型参数。
当通过通信通道发送完整对象时，它们将使用JSON进行序列化。
您可以使用Fiddler等工具监视方法调用。
创建应用程序
首先创建一个空的ASP.NET Web项目，右键单击以添加SignalR，确保您的项目针对.NET 4.5或更高版本：
选择SignalR：
或者您只需在包管理器控制台中输入：
PM> install-package Microsoft.AspNet.SignalR
PM> install-Package jQuery.UI.Combined
PM> install-Package Microsoft.Web.Infrastructure接下来，将一个名为Startup的类添加到应用程序中，该类在应用程序启动时映射SignalR集线器：
using Microsoft.AspNet.SignalR;
using Microsoft.Owin;
using Owin;
[assembly: OwinStartup(typeof(CodeProjectSignalRSample.Startup))]
namespace CodeProjectSignalRSample
{
public class Startup
{
public void Configuration(IAppBuilder app)
{
var hubConfiguration = new HubConfiguration();
hubConfiguration.EnableDetailedErrors = true;
app.MapSignalR();
}
}
}如果您还没有，请添加以下SignalR集线器类：
using Microsoft.AspNet.SignalR;
using Newtonsoft.Json;
namespace CodeProjectSignalRSample
{
public class MyHub : Hub
{
public void UpdateModel(ShapeModel clientModel)
{
clientModel.LastUpdatedBy = Context.ConnectionId;
// Update the shape model within our broadcaster
Clients.AllExcept(clientModel.LastUpdatedBy).updateShape(clientModel);
}
}
public class ShapeModel
{
// We declare Left and Top as lowercase with
// JsonProperty to sync the client and server models
[JsonProperty("left")]
public double Left { get; set; }
[JsonProperty("top")]
public double Top { get; set; }
// We don't want the client to get the "LastUpdatedBy" property
[JsonIgnore]
public string LastUpdatedBy { get; set; }
}
}客户端可以直接调用UpdateModel方法，然后将其广播到所有连接的客户端。它使用JSON自动序列化。
现在通过向解决方案添加HTML页面来添加客户端：
<!DOCTYPE html>
<html>
<head>
<title>SignalR Demo</title>
<style>
#shape {
width: 100px;
height: 100px;
background-color: #FF0000;
}
</style>
</head>
<body>
<script src="Scripts/jquery-1.10.2.min.js"></script>
<script src="Scripts/jquery-ui-1.10.4.min.js"></script>
<script src="Scripts/jquery.signalR-2.1.0.js"></script>
<script src="/signalr/hubs"></script>
<script>
$(function () {
var moveShapeHub = $.connection.myHub,
$shape = $("#shape"),
shapeModel = {
left: 0,
top: 0
};
MyHub.client.updateShape = function (model) {
shapeModel = model;
$shape.css({ left: model.left, top: model.top });
};
$.connection.hub.start().done(function () {
$shape.draggable({
drag: function () {
shapeModel = $shape.offset();
MyHub.server.updateModel(shapeModel);
}
});
});
});
</script>
<div id="shape" />
</body>
</html>另外，请确保您的web.config文件包含以下内容：
<?xml version="1.0" encoding="utf-8"?>
<!--
For more information on how to configure your ASP.NET application, please visit
http://go.microsoft.com/fwlink/?LinkId=169433
-->
<configuration>
<system.web>
<compilation debug="true" targetFramework="4.5" />
<httpRuntime targetFramework="4.5" />
</system.web>
</configuration>启动应用程序，然后将URL复制到浏览器的新实例中。尝试移动形状。
添加客户端循环
在每次鼠标移动时发送位置会产生大量网络流量，因此您可以通过将此代码放入HTML文件来限制它：
<!DOCTYPE html>
<html>
<head>
<title>SignalR Demo</title>
<style>
#shape {
width: 100px;
height: 100px;
background-color: #FF0000;
}
</style>
</head>
<body>
<script src="Scripts/jquery-1.6.4.min.js"></script>
<script src="Scripts/jquery-ui-1.11.3.min.js"></script>
<script src="Scripts/jquery.signalR-2.2.0.js"></script>
<script src="/signalr/hubs"></script>
<script>
$(function () {
var moveShapeHub = $.connection.myHub,
$shape = $("#shape"),
// Send a maximum of 10 messages per second
// (mouse movements trigger a lot of messages)
messageFrequency = 10,
// Determine how often to send messages in
// time to abide by the messageFrequency
updateRate = 1000 / messageFrequency,
shapeModel = {
left: 0,
top: 0
},
moved = false;
moveShapeHub.client.updateShape = function (model) {
shapeModel = model;
$shape.css({ left: model.left, top: model.top });
};
$.connection.hub.start().done(function () {
$shape.draggable({
drag: function () {
shapeModel = $shape.offset();
moved = true;
}
});
// Start the client side server update interval
setInterval(updateServerModel, updateRate);
});
function updateServerModel() {
// Only update server if we have a new movement
if (moved) {
moveShapeHub.server.updateModel(shapeModel);
moved = false;
}
}
});
</script>
<div id="shape" />
</body>
</html>添加服务器循环
将以下代码添加到集线器还可以减少服务器端的流量：
using System;
using System.Threading;
using Microsoft.AspNet.SignalR;
using Newtonsoft.Json;
namespace CodeProjectSignalRSample
{
public class Broadcaster
{
private readonly static Lazy
_instance =
new Lazy
(() => new Broadcaster());
// We're going to broadcast to all clients a maximum of 25 times per second
private readonly TimeSpan BroadcastInterval =
TimeSpan.FromMilliseconds(40);
private readonly IHubContext _hubContext;
private Timer _broadcastLoop;
private ShapeModel _model;
private bool _modelUpdated;
public Broadcaster()
{
// Save our hub context so we can easily use it
// to send to its connected clients
_hubContext = GlobalHost.ConnectionManager.GetHubContext<myhub>();
_model = new ShapeModel();
_modelUpdated = false;
// Start the broadcast loop
_broadcastLoop = new Timer(
BroadcastShape,
null,
BroadcastInterval,
BroadcastInterval);
}
public void BroadcastShape(object state)
{
// No need to send anything if our model hasn't changed
if (_modelUpdated)
{
// This is how we can access the Clients property
// in a static hub method or outside of the hub entirely
_hubContext.Clients.AllExcept(_model.LastUpdatedBy).updateShape(_model);
_modelUpdated = false;
}
}
public void UpdateShape(ShapeModel clientModel)
{
_model = clientModel;
_modelUpdated = true;
}
public static Broadcaster Instance
{
get
{
return _instance.Value;
}
}
}
public class MyHub : Hub
{
private Broadcaster _broadcaster;
public MyHub()
: this(Broadcaster.Instance)
{
}
public MyHub(Broadcaster broadcaster)
{
_broadcaster = broadcaster;
}
public void UpdateModel(ShapeModel clientModel)
{
clientModel.LastUpdatedBy = Context.ConnectionId;
// Update the shape model within our broadcaster
Clients.AllExcept(clientModel.LastUpdatedBy).updateShape(clientModel);
}
}
public class ShapeModel
{
// We declare Left and Top as lowercase with
// JsonProperty to sync the client and server models
[JsonProperty("left")]
public double Left { get; set; }
[JsonProperty("top")]
public double Top { get; set; }
// We don't want the client to get the "LastUpdatedBy" property
[JsonIgnore]
public string LastUpdatedBy { get; set; }
}
}向客户端添加平滑动画
添加以下代码以使形状在1000毫秒的过程中从旧位置移动到新位置：
<!DOCTYPE html>
<html>
<head>
<title>SignalR Demo</title>
<style>
#shape {
width: 100px;
height: 100px;
background-color: #FF0000;
}
</style>
</head>
<body>
<script src="Scripts/jquery-1.6.4.min.js"></script>
<script src="Scripts/jquery-ui-1.11.3.min.js"></script>
<script src="Scripts/jquery.signalR-2.2.0.js"></script>
<script src="/signalr/hubs"></script>
<script>
$(function () {
var moveShapeHub = $.connection.myHub,
$shape = $("#shape"),
// Send a maximum of 10 messages per second
// (mouse movements trigger a lot of messages)
messageFrequency = 10,
// Determine how often to send messages in
// time to abide by the messageFrequency
updateRate = 1000 / messageFrequency,
shapeModel = {
left: 0,
top: 0
},
moved = false;
moveShapeHub.client.updateShape = function (model) {
shapeModel = model;
$shape.css({ left: model.left, top: model.top });
};
$.connection.hub.start().done(function () {
$shape.draggable({
drag: function () {
shapeModel = $shape.offset();
moved = true;
moveShapeHub.client.updateShape = function (model) {
shapeModel = model;
// Gradually move the shape towards the new location (interpolate)
// The updateRate is used as the duration because by the time
// we get to the next location we want to be at the "last" location
// We also clear the animation queue so that we start a new
// animation and don't lag behind.
$shape.animate(shapeModel, { duration: updateRate, queue: false });
}
});
// Start the client side server update interval
setInterval(updateServerModel, updateRate);
});
function updateServerModel() {
// Only update server if we have a new movement
if (moved) {
moveShapeHub.server.updateModel(shapeModel);
moved = false;
}
}
});
</script>
<div id="shape" />
</body>
</html>参考
- Learn About ASP.NET SignalR
- Sample SignalR Game ShootR
- SignalR Source Code
- Building Web Apps with ASP.NET Jump Start: (08) Real-time Communication with SignalR
- OWIN and Katana
- ASP.NET SignalR Hubs API Guide - JavaScript Client
原文地址：https://www.codeproject.com/Tips/880963/Introduction-to-SignalR