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重新想象 Windows 8 Store Apps (68) - 后台任务: 控制通道(ControlChannel)



作者:webabcd


介绍
重新想象 Windows 8 Store Apps 之 后台任务

  • 控制通道(ControlChannel)



示例
1、客户端与服务端做 ControlChannel 通信的关键代码
ControlChannelHelper/AppContext.cs

/*
 * 本例通过全局静态变量来实现 app 与 task 的信息共享,以便后台任务可以获取到 app 中的相关信息
 * 
 * 注:
 * 也可以通过 Windows.ApplicationModel.Core.CoreApplication.Properties 保存数据,以实现 app 与 task 的信息共享
 */

using System.Collections.Concurrent;
using Windows.Networking.Sockets;

namespace ControlChannelHelper
{
    public class AppContext
    {
        /// <summary>
        /// 从 ControlChannel 接收到的数据
        /// </summary>
        public static ConcurrentQueue<string> MessageQueue = new ConcurrentQueue<string>();

        /// <summary>
        /// 客户端 socket
        /// </summary>
        public static StreamSocket ClientSocket;
    }
}

ControlChannelHelper/SocketControlChannel.cs

/*
 * 实现一个 socket tcp 通信的 ControlChannel,client 将在此 ControlChannel 中实时接收数据
 * 
 * 注:
 * win8 client 和 socket server 不能部署在同一台机器上,否则会抛出异常:{参考的对象类型不支持尝试的操作。 (异常来自 HRESULT:0x8007273D)}
 */

using System;
using System.Threading.Tasks;
using Windows.ApplicationModel.Background;
using Windows.Foundation;
using Windows.Networking;
using Windows.Networking.Sockets;
using Windows.Storage.Streams;

namespace ControlChannelHelper
{
    public class SocketControlChannel : IDisposable
    {
        // ControlChannel
        public ControlChannelTrigger Channel { get; set; }

        // 客户端 socket
        private StreamSocket _socket;
        // 用于发送数据
        private DataWriter _dataWriter;
        // 用于接收数据
        private DataReader _dataReader;

        // 向服务端发送心跳的间隔时间,单位为分钟,最小 15 分钟
        private uint _serverKeepAliveInterval = 15;
        // ControlChannel 的标识
        private string _channelId = "myControlChannel";

        public SocketControlChannel()
        {

        }

        public async Task<string> CreateChannel()
        {
            Dispose();

            try
            {
                // 实例化一个 ControlChannel
                Channel = new ControlChannelTrigger(_channelId, _serverKeepAliveInterval, ControlChannelTriggerResourceType.RequestHardwareSlot);
            }
            catch (Exception ex)
            {
                Dispose();
                return "控制通道创建失败:" + ex.ToString();
            }

            // 注册用于向服务端 socket 发送心跳的后台任务,需要在 manifest 中做相关配置
            var keepAliveBuilder = new BackgroundTaskBuilder();
            keepAliveBuilder.Name = "myControlChannelKeepAlive";
            // 注:如果走的是 WebSocket 协议,则系统已经为其内置了发送心跳的逻辑,此处直接指定为 Windows.Networking.Sockets.WebSocketKeepAlive 即可
            keepAliveBuilder.TaskEntryPoint = "BackgroundTaskLib.ControlChannelKeepAlive";
            keepAliveBuilder.SetTrigger(Channel.KeepAliveTrigger); // 到了发送心跳的间隔时间时则触发,本例是 15 分钟
            keepAliveBuilder.Register();

            // 注册用于向用户显示通知的后台任务,需要在 manifest 中做相关配置
            var pushNotifyBuilder = new BackgroundTaskBuilder();
            pushNotifyBuilder.Name = "myControlChannelPushNotification";
            pushNotifyBuilder.TaskEntryPoint = "BackgroundTaskLib.ControlChannelPushNotification";
            pushNotifyBuilder.SetTrigger(Channel.PushNotificationTrigger); // 在 ControlChannel 中收到了推送过来的数据时则触发
            pushNotifyBuilder.Register();

            try
            {
                _socket = new StreamSocket();
                AppContext.ClientSocket = _socket;

                // 在 ControlChannel 中通过指定的 StreamSocket 通信
                Channel.UsingTransport(_socket);

                // client socket 连接 server socket
                await _socket.ConnectAsync(new HostName("192.168.6.204"), "3366");

                // 开始等待 ControlChannel 中推送过来的数据,如果 win8 client 和 socket server 部署在同一台机器上,则此处会抛出异常
                ControlChannelTriggerStatus status = Channel.WaitForPushEnabled();

                if (status != ControlChannelTriggerStatus.HardwareSlotAllocated && status != ControlChannelTriggerStatus.SoftwareSlotAllocated)
                    return "控制通道创建失败:" + status.ToString();

                // 发送数据到服务端
                _dataWriter = new DataWriter(_socket.OutputStream);
                string message = "hello " + DateTime.Now.ToString("hh:mm:ss") + "^";
                _dataWriter.WriteString(message);
                await _dataWriter.StoreAsync();

                // 接收数据
                ReceiveData();
            }
            catch (Exception ex)
            {
                Dispose();
                return "控制通道创建失败:" + ex.ToString();
            }

            return "ok";
        }

        // 开始接收此次数据
        private void ReceiveData()
        {
            uint maxBufferLength = 256;

            try
            {
                var buffer = new Windows.Storage.Streams.Buffer(maxBufferLength);
                var asyncOperation = _socket.InputStream.ReadAsync(buffer, maxBufferLength, InputStreamOptions.Partial);
                asyncOperation.Completed = (IAsyncOperationWithProgress<IBuffer, uint> asyncInfo, AsyncStatus asyncStatus) =>
                {
                    switch (asyncStatus)
                    {
                        case AsyncStatus.Completed:
                        case AsyncStatus.Error:
                            try
                            {
                                IBuffer bufferRead = asyncInfo.GetResults();
                                uint bytesRead = bufferRead.Length;
                                _dataReader = DataReader.FromBuffer(bufferRead);

                                // 此次数据接收完毕
                                ReceiveCompleted(bytesRead);
                            }
                            catch (Exception ex)
                            {
                                AppContext.MessageQueue.Enqueue(ex.ToString());
                            }
                            break;
                        case AsyncStatus.Canceled:
                            AppContext.MessageQueue.Enqueue("接收数据时被取消了");
                            break;
                    }
                };
            }
            catch (Exception ex)
            {
                AppContext.MessageQueue.Enqueue(ex.ToString());
            }
        }

        public void ReceiveCompleted(uint bytesRead)
        {
            // 获取此次接收到的数据
            uint bufferLength = _dataReader.UnconsumedBufferLength;
            string message = _dataReader.ReadString(bufferLength);

            // 将接收到的数据放到内存中,由 PushNotificationTrigger 触发的后台任进行处理(当然也可以在此处处理)
            AppContext.MessageQueue.Enqueue(message);

            // 开始接收下一次数据
            ReceiveData();
        }

        // 释放资源
        public void Dispose()
        {
            lock (this)
            {
                if (_dataWriter != null)
                {
                    try
                    {
                        _dataWriter.DetachStream();
                        _dataWriter = null;
                    }
                    catch (Exception ex)
                    {

                    }
                }

                if (_dataReader != null)
                {
                    try
                    {
                        _dataReader.DetachStream();
                        _dataReader = null;
                    }
                    catch (Exception exp)
                    {

                    }
                }

                if (_socket != null)
                {
                    _socket.Dispose();
                    _socket = null;
                }

                if (Channel != null)
                {
                    Channel.Dispose();
                    Channel = null;
                }
            }
        }
    }
}


2、客户端辅助类
BackgroundTaskLib/ControlChannelKeepAlive.cs

/*
 * 用于向服务端 socket 发送心跳的后台任务
 * 
 * 注:
 * 如果走的是 WebSocket 协议,则系统已经为其内置了发送心跳的逻辑
 * 只需要将 BackgroundTaskBuilder.TaskEntryPoint 设置为 Windows.Networking.Sockets.WebSocketKeepAlive 即可,而不需要再自定义此后台任务
 */

using ControlChannelHelper;
using System;
using Windows.ApplicationModel.Background;
using Windows.Networking.Sockets;
using Windows.Storage.Streams;

namespace BackgroundTaskLib
{
    public sealed class ControlChannelKeepAlive : IBackgroundTask
    {
        public void Run(IBackgroundTaskInstance taskInstance)
        {
            if (taskInstance == null)
                return;

            // 获取 ControlChannel
            var channelEventArgs = taskInstance.TriggerDetails as IControlChannelTriggerEventDetails;
            ControlChannelTrigger channel = channelEventArgs.ControlChannelTrigger;

            if (channel == null)
                return;

            string channelId = channel.ControlChannelTriggerId;

            // 发送心跳
            SendData();
        }

        private async void SendData()
        {
            // 发送心跳到 server socket
            DataWriter dataWriter = new DataWriter(AppContext.ClientSocket.OutputStream);
            string message = "hello " + DateTime.Now.ToString("hh:mm:ss") + "^";
            dataWriter.WriteString(message);
            await dataWriter.StoreAsync();
        }
    }
}

BackgroundTaskLib/ControlChannelPushNotification.cs

/*
 * 用于向用户显示通知的后台任务,需要在 manifest 中做相关配置
 */

using ControlChannelHelper;
using NotificationsExtensions.ToastContent;
using System;
using Windows.ApplicationModel.Background;
using Windows.Networking.Sockets;
using Windows.UI.Notifications;

namespace BackgroundTaskLib
{
    public sealed class ControlChannelPushNotification : IBackgroundTask
    {
        public void Run(IBackgroundTaskInstance taskInstance)
        {
            if (taskInstance == null)
                return;

            // 获取 ControlChannel
            var channelEventArgs = taskInstance.TriggerDetails as IControlChannelTriggerEventDetails;
            ControlChannelTrigger channel = channelEventArgs.ControlChannelTrigger;

            if (channel == null)
                return;

            string channelId = channel.ControlChannelTriggerId;

            try
            {
                string messageReceived;

                // 将从 ControlChannel 中接收到的信息,以 toast 的形式弹出
                while (AppContext.MessageQueue.Count > 0)
                {
                    bool result = AppContext.MessageQueue.TryDequeue(out messageReceived);
                    if (result)
                    {
                        IToastText01 templateContent = ToastContentFactory.CreateToastText01();
                        templateContent.TextBodyWrap.Text = messageReceived;
                        templateContent.Duration = ToastDuration.Short; 
                        IToastNotificationContent toastContent = templateContent;
                        ToastNotification toast = toastContent.CreateNotification();

                        ToastNotifier toastNotifier = ToastNotificationManager.CreateToastNotifier();
                        toastNotifier.Show(toast);
                    }
                }
            }
            catch (Exception ex)
            {

            }
        }
    }
}


3、客户端
BackgroundTask/ControlChannel.xaml

<Page
    x:Class="XamlDemo.BackgroundTask.ControlChannel"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.BackgroundTask"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <StackPanel Margin="120 0 0 0">
            
            <TextBlock Name="lblMsg" FontSize="14.667" />
            
            <Button Name="btnCreateChannel" Content="创建一个 ControlChannel" Margin="0 10 0 0" Click="btnCreateChannel_Click" />
            
        </StackPanel>
    </Grid>
</Page>

BackgroundTask/ControlChannel.xaml.cs

/*
 * 演示如何创建一个基于 socket tcp 通信的 ControlChannel,client 将在此 ControlChannel 中实时接收数据
 * 
 * 注:
 * 不能在模拟器中运行
 * RTC - Real Time Communication 实时通信
 * win8 client 和 socket server 不能部署在同一台机器上,否则会抛出异常:{参考的对象类型不支持尝试的操作。 (异常来自 HRESULT:0x8007273D)}
 */

using System;
using ControlChannelHelper;
using Windows.ApplicationModel.Background;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Popups;

namespace XamlDemo.BackgroundTask
{
    public sealed partial class ControlChannel : Page
    {
        public ControlChannel()
        {
            this.InitializeComponent();
        }

        private async void btnCreateChannel_Click(object sender, RoutedEventArgs e)
        {
            // 如果 app 在锁屏上,则可以通过 ControlChannelTrigger 触发指定的后台任务
            BackgroundAccessStatus status = BackgroundExecutionManager.GetAccessStatus();
            if (status == BackgroundAccessStatus.Unspecified)
            {
                status = await BackgroundExecutionManager.RequestAccessAsync();
            }
            if (status == BackgroundAccessStatus.Denied)
            {
                await new MessageDialog("请先将此 app 添加到锁屏").ShowAsync();
                return;
            }

            // 创建一个基于 socket tcp 通信的 ControlChannel,相关代码参见:ControlChannelHelper 项目
            SocketControlChannel channel = new SocketControlChannel();
            string result = await channel.CreateChannel();

            lblMsg.Text = result;
        }
    }
}


4、服务端
SocketServerTcp/ClientSocketPacket.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace SocketServerTcp
{
    /// <summary>
    /// 对客户端 Socket 及其他相关信息做一个封装
    /// </summary>
    public class ClientSocketPacket
    {
        /// <summary>
        /// 客户端 Socket
        /// </summary>
        public System.Net.Sockets.Socket Socket { get; set; }

        private byte[] _buffer;
        /// <summary>
        /// 为该客户端 Socket 开辟的缓冲区
        /// </summary>
        public byte[] Buffer
        {
            get
            {
                if (_buffer == null)
                    _buffer = new byte[64];

                return _buffer;
            }
        }

        private List<byte> _receivedByte;
        /// <summary>
        /// 客户端 Socket 发过来的信息的字节集合
        /// </summary>
        public List<byte> ReceivedByte
        {
            get
            {
                if (_receivedByte == null)
                    _receivedByte = new List<byte>();

                return _receivedByte;
            }
        }
    }
}

SocketServerTcp/Main.cs

/*
 * 从以前写的 wp7 demo 中直接复制过来的,用于演示如何通过 ControlChannel 实时地将信息以 socket tcp 的方式推送到 win8 客户端
 * 
 * 注:
 * 本例通过一个约定结束符来判断是否接收完整,其仅用于演示,实际项目中请用自定义协议。可参见:XamlDemo/Communication/TcpDemo.xaml.cs
 */

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

using System.Net.Sockets;
using System.Net;
using System.Threading;
using System.IO;

namespace SocketServerTcp
{
    public partial class Main : Form
    {
        SynchronizationContext _syncContext;

        System.Timers.Timer _timer;

        // 信息结束符,用于判断是否完整地读取了客户端发过来的信息,要与客户端的信息结束符相对应(本例只用于演示,实际项目中请用自定义协议)
        private string _endMarker = "^";

        // 服务端监听的 socket
        private Socket _listener;

        // 实例化 ManualResetEvent,设置其初始状态为无信号
        private ManualResetEvent _signal = new ManualResetEvent(false);

        // 客户端 Socket 列表
        private List<ClientSocketPacket> _clientList = new List<ClientSocketPacket>();

        public Main()
        {
            InitializeComponent();

            // UI 线程
            _syncContext = SynchronizationContext.Current;

            // 启动后台线程去运行 Socket 服务
            Thread thread = new Thread(new ThreadStart(LaunchSocketServer));
            thread.IsBackground = true;
            thread.Start();
        }

        private void LaunchSocketServer()
        {
            // 每 10 秒运行一次计时器所指定的方法,群发信息
            _timer = new System.Timers.Timer();
            _timer.Interval = 10000d;
            _timer.Elapsed += new System.Timers.ElapsedEventHandler(_timer_Elapsed);
            _timer.Start();

            // TCP 方式监听 3366 端口
            _listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            _listener.Bind(new IPEndPoint(IPAddress.Any, 3366));
            // 指定等待连接队列中允许的最大数
            _listener.Listen(10);


            while (true)
            {
                // 设置为无信号
                _signal.Reset();

                // 开始接受客户端传入的连接
                _listener.BeginAccept(new AsyncCallback(OnClientConnect), null);

                // 阻塞当前线程,直至有信号为止
                _signal.WaitOne();
            }
        }

        private void _timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
        {
            // 每 10 秒给所有连入的客户端发送一次消息
            SendData(string.Format("webabcd 对所有人说:大家好! 【信息来自服务端 {0}】", DateTime.Now.ToString("hh:mm:ss")));
        }

        private void OnClientConnect(IAsyncResult async)
        {
            ClientSocketPacket client = new ClientSocketPacket();
            // 完成接受客户端传入的连接的这个异步操作,并返回客户端连入的 socket
            client.Socket = _listener.EndAccept(async);

            // 将客户端连入的 Socket 放进客户端 Socket 列表
            _clientList.Add(client);

            OutputMessage(((IPEndPoint)client.Socket.LocalEndPoint).Address + " 连入了服务器");
            SendData("一个新的客户端已经成功连入服务器。。。 【信息来自服务端】");

            try
            {
                // 开始接收客户端传入的数据
                client.Socket.BeginReceive(client.Buffer, 0, client.Buffer.Length, SocketFlags.None, new AsyncCallback(OnDataReceived), client);
            }
            catch (SocketException ex)
            {
                // 处理异常
                HandleException(client, ex);
            }

            // 设置为有信号
            _signal.Set();
        }

        private void OnDataReceived(IAsyncResult async)
        {
            ClientSocketPacket client = async.AsyncState as ClientSocketPacket;

            int count = 0;

            try
            {
                // 完成接收数据的这个异步操作,并返回接收的字节数
                if (client.Socket.Connected)
                    count = client.Socket.EndReceive(async);
            }
            catch (SocketException ex)
            {
                HandleException(client, ex);
            }

            // 把接收到的数据添加进收到的字节集合内
            // 本例采用 UTF8 编码,中文占用 3 字节,英文等字符与 ASCII 相同
            foreach (byte b in client.Buffer.Take(count))
            {
                if (b == 0) continue; // 如果是空字节则不做处理('\0')

                client.ReceivedByte.Add(b);
            }

            // 把当前接收到的数据转换为字符串。用于判断是否包含自定义的结束符
            string receivedString = UTF8Encoding.UTF8.GetString(client.Buffer, 0, count);

            // 如果该 Socket 在网络缓冲区中没有排队的数据 并且 接收到的数据中有自定义的结束符时
            if (client.Socket.Connected && client.Socket.Available == 0 && receivedString.Contains(_endMarker))
            {
                // 把收到的字节集合转换成字符串(去掉自定义结束符)
                // 然后清除掉字节集合中的内容,以准备接收用户发送的下一条信息
                string content = UTF8Encoding.UTF8.GetString(client.ReceivedByte.ToArray());
                content = content.Replace(_endMarker, "");
                client.ReceivedByte.Clear();

                // 发送数据到所有连入的客户端,并在服务端做记录
                SendData(content);
                OutputMessage(content);
            }

            try
            {
                // 继续开始接收客户端传入的数据
                if (client.Socket.Connected)
                    client.Socket.BeginReceive(client.Buffer, 0, client.Buffer.Length, 0, new AsyncCallback(OnDataReceived), client);
            }
            catch (SocketException ex)
            {
                HandleException(client, ex);
            }
        }

        /// <summary>
        /// 发送数据到所有连入的客户端
        /// </summary>
        /// <param name="data">需要发送的数据</param>
        private void SendData(string data)
        {
            byte[] byteData = UTF8Encoding.UTF8.GetBytes(data);

            foreach (ClientSocketPacket client in _clientList)
            {
                if (client.Socket.Connected)
                {
                    try
                    {
                        // 如果某客户端 Socket 是连接状态,则向其发送数据
                        client.Socket.BeginSend(byteData, 0, byteData.Length, SocketFlags.None, new AsyncCallback(OnDataSent), client);
                    }
                    catch (SocketException ex)
                    {
                        HandleException(client, ex);
                    }
                }
                else
                {
                    // 某 Socket 断开了连接的话则将其关闭,并将其清除出客户端 Socket 列表
                    // 也就是说每次向所有客户端发送消息的时候,都会从客户端 Socket 集合中清除掉已经关闭了连接的 Socket
                    client.Socket.Close();
                    _clientList.Remove(client);
                }
            }
        }

        private void OnDataSent(IAsyncResult async)
        {
            ClientSocketPacket client = async.AsyncState as ClientSocketPacket;

            try
            {
                // 完成将信息发送到客户端的这个异步操作
                int sentBytesCount = client.Socket.EndSend(async);
            }
            catch (SocketException ex)
            {
                HandleException(client, ex);
            }
        }

        /// <summary>
        /// 处理 SocketException 异常
        /// </summary>
        /// <param name="client">导致异常的 ClientSocketPacket</param>
        /// <param name="ex">SocketException</param>
        private void HandleException(ClientSocketPacket client, SocketException ex)
        {
            // 在服务端记录异常信息,关闭导致异常的 Socket,并将其清除出客户端 Socket 列表
            OutputMessage(client.Socket.RemoteEndPoint.ToString() + " - " + ex.Message);
            client.Socket.Close();
            _clientList.Remove(client);
        }

        // 在 UI 上输出指定信息
        private void OutputMessage(string data)
        {
            _syncContext.Post((p) => { txtMsg.Text += p.ToString() + "\r\n"; }, data);
        }
    }
}



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