检测串口插入/移除

Posted 2023-02-15

【中文标题】检测串口插入/移除

【英文标题】：Detect serial port insertion/removal

【发布时间】：2011-05-11 02:08:51

【问题描述】：

我正在连接一个可以随时插入或移除的 USB 转串口。我发现我可以使用WMI（尤其是使用WMI Code Creator）来查询PC 中的设备更改。

在下面生成的 sn-p 中，订阅了 Win32_DeviceChangeEvent。但是，此事件不会显示 哪个设备（例如 USB、串行端口等）导致了该事件。有没有办法只在插入或移除串行端口时接收通知？

澄清一下，代码的重点不是检测串口的开启/关闭，而是检测是否有新端口已添加到计算机或之前的端口已删除。

using System;
using System.Management;
using System.Windows.Forms;

namespace WMISample

    public class WMIReceiveEvent
    
        public WMIReceiveEvent()
        
            try
            
                WqlEventQuery query = new WqlEventQuery(
                    "SELECT * FROM Win32_DeviceChangeEvent");

                ManagementEventWatcher watcher = new ManagementEventWatcher(query);
                Console.WriteLine("Waiting for an event...");

                watcher.EventArrived += 
                    new EventArrivedEventHandler(
                    HandleEvent);

                // Start listening for events
                watcher.Start();

                // Do something while waiting for events
                System.Threading.Thread.Sleep(10000);

                // Stop listening for events
                watcher.Stop();
                return;
            
            catch(ManagementException err)
            
                MessageBox.Show("An error occurred while trying to receive an event: " + err.Message);
            
        

        private void HandleEvent(object sender,
            EventArrivedEventArgs e)
        
            Console.WriteLine("Win32_DeviceChangeEvent event occurred.");
        

        public static void Main()
        
            WMIReceiveEvent receiveEvent = new WMIReceiveEvent();
            return;
        

    

【参考方案1】：

没有。去看看 SerialPort.GetPortNames() 发生了什么。在窗口中收听WM_DEVICECHANGE 消息可以为您提供更好的信息。

【参考方案2】：

这是我前段时间编写的DeviceChangeEvents 通知类的精简版，尽管我从未完全完成它。我去掉了除了 PortArrived 事件之外的所有内容，因为否则它非常丑陋。

using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows.Forms;

public sealed class PortArrivalEventArgs : EventArgs

    public string Name  get; private set; 
    public PortArrivalEventArgs(string name)  Name = name; 


public static class DeviceChangeEvents

    #region Events

    #region PortArrived
    private static object PortArrivedEvent = new Object();
    public static event EventHandler<PortArrivalEventArgs> PortArrived
    
        add  AddEvent(PortArrivedEvent, value); 
        remove  RemoveEvent(PortArrivedEvent, value); 
    
    private static void FirePortArrived(IntPtr lParam)
    
        EventHandler<PortArrivalEventArgs> handler
            = (EventHandler<PortArrivalEventArgs>)events[PortArrivedEvent];
        if (handler != null)
        
            string portName = Marshal.PtrToStringAuto((IntPtr)((long)lParam + 12));
            handler(null, new PortArrivalEventArgs(portName));
        
    
    #endregion

    #endregion

    #region Internal

    private static EventHandlerList events = new EventHandlerList();
    private static MessageWindow messageWindow = null;

    private static void AddEvent(object key, Delegate value)
    
        events.AddHandler(key, value);
        if (messageWindow == null)
            messageWindow = new MessageWindow();
    

    private static void RemoveEvent(object key, Delegate value)
    
        events.RemoveHandler(key, value);

        // In the more complete version of DeviceChangedEvents, System.ComponentModel.EventHandlerList
        //  is replaced by an identical event storage object which exposes a count of the number of
        //  handlers installed. It also removes empty handler stubs. Both of these are required
        //  to safely destroy the message window when the last handler is removed.

        //if (messageWindow != null && events.Count == 0)
        //    messageWindow.DestroyHandle();
    

    #endregion

    private sealed class MessageWindow : NativeWindow
    
        public MessageWindow()
        
            CreateParams cp = new CreateParams();
            cp.Caption = GetType().FullName;
            // NOTE that you cannot use a "message window" for this broadcast message
            //if (Environment.OSVersion.Platform == PlatformID.Win32NT)
            //  cp.Parent = (IntPtr)(-3); // HWND_MESSAGE
            //Debug.WriteLine("Creating MessageWindow " + cp.Caption);
            CreateHandle(cp);
        

        const int WM_DESTROY = 0x02;
        const int WM_DEVICECHANGE = 0x219;

        enum DBT
        
            DEVICEARRIVAL = 0x8000,
        

        protected override void WndProc(ref Message m)
        
            if (m.Msg == WM_DESTROY)
            
                messageWindow = null;
            
            else if (m.Msg == WM_DEVICECHANGE)
            
                DBT changeType = (DBT)m.WParam;
                int deviceType = m.LParam == IntPtr.Zero ? 0 : Marshal.ReadInt32(m.LParam, 4);

                Debug.WriteLine(String.Format("WM_DEVICECHANGE changeType = 0, deviceType = 1", changeType, deviceType));

                switch (changeType)
                
                    case DBT.DEVICEARRIVAL:
                        switch (deviceType)
                        
                            case 3: // DBT_DEVTYP_PORT
                                FirePortArrived(m.LParam);
                                break;
                        
                        break;
                
            

            base.WndProc(ref m);
        
    

【讨论】：

感谢您澄清@Hans 所说的“在窗口中侦听 WM_DEVICECHANGE 消息”的含义 - 我不知道。但是必须有一个 NativeWindow 和非托管代码并没有真正吸引我。

代码的每一行都会调用非托管代码。没有所谓的“纯”.NET 应用程序。如果不与操作系统交互，任何应用程序都无法执行有用的工作。

如果您不喜欢 NativeWindow（这没有任何意义，因为所有 System.Windows.Forms.Control 对象都基于 NativeWindow），您可以简单地覆盖主窗口的 WndProc。上述类的目的是自己封装消息。

我无意冒犯，但使用 Marshal 类中的任何内容都意味着使用非托管代码 (msdn.microsoft.com/en-us/library/…)。另外，我正在使用控制台应用程序，因此没有“主窗口”。

如果您想在控制台应用程序中使用 WM_DEVICECHANGE，您可以使用消息泵和窗口启动线程。我没有冒犯您的评论，我的问题是人们对“不安全”代码的厌恶。 .NET Framework 充满了不安全的代码。这是无法避免的，因此任何对它的厌恶都是不合逻辑的。

【参考方案3】：

我最终使用 WMI 和 @Hans 的建议来检查哪些串行端口是新的/缺少的。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Diagnostics.Contracts;
using System.IO.Ports;
using System.Management;

public static class SerialPortService

    private static SerialPort _serialPort;

    private static string[] _serialPorts;

    private static ManagementEventWatcher arrival;

    private static ManagementEventWatcher removal;

    static SerialPortService()
    
        _serialPorts = GetAvailableSerialPorts();
        MonitorDeviceChanges();
    

    /// <summary>
    /// If this method isn't called, an InvalidComObjectException will be thrown (like below):
    /// System.Runtime.InteropServices.InvalidComObjectException was unhandled
    ///Message=COM object that has been separated from its underlying RCW cannot be used.
    ///Source=mscorlib
    ///StackTrace:
    ///     at System.StubHelpers.StubHelpers.StubRegisterRCW(Object pThis, IntPtr pThread)
    ///     at System.Management.IWbemServices.CancelAsyncCall_(IWbemObjectSink pSink)
    ///     at System.Management.SinkForEventQuery.Cancel()
    ///     at System.Management.ManagementEventWatcher.Stop()
    ///     at System.Management.ManagementEventWatcher.Finalize()
    ///InnerException: 
    /// </summary>
    public static void CleanUp()
    
        arrival.Stop();
        removal.Stop();
    

    public static event EventHandler<PortsChangedArgs> PortsChanged;

    private static void MonitorDeviceChanges()
    
        try
        
            var deviceArrivalQuery = new WqlEventQuery("SELECT * FROM Win32_DeviceChangeEvent WHERE EventType = 2");
            var deviceRemovalQuery = new WqlEventQuery("SELECT * FROM Win32_DeviceChangeEvent WHERE EventType = 3");

            arrival = new ManagementEventWatcher(deviceArrivalQuery);
            removal = new ManagementEventWatcher(deviceRemovalQuery);

            arrival.EventArrived += (o, args) => RaisePortsChangedIfNecessary(EventType.Insertion);
            removal.EventArrived += (sender, eventArgs) => RaisePortsChangedIfNecessary(EventType.Removal);

            // Start listening for events
            arrival.Start();
            removal.Start();
        
        catch (ManagementException err)
        

        
    

    private static void RaisePortsChangedIfNecessary(EventType eventType)
    
        lock (_serialPorts)
        
            var availableSerialPorts = GetAvailableSerialPorts();
            if (!_serialPorts.SequenceEqual(availableSerialPorts))
            
                _serialPorts = availableSerialPorts;
                PortsChanged.Raise(null, new PortsChangedArgs(eventType, _serialPorts));
            
        
    

    public static string[] GetAvailableSerialPorts()
    
        return SerialPort.GetPortNames();
    


public enum EventType

    Insertion,
    Removal,


public class PortsChangedArgs : EventArgs

    private readonly EventType _eventType;

    private readonly string[] _serialPorts;

    public PortsChangedArgs(EventType eventType, string[] serialPorts)
    
        _eventType = eventType;
        _serialPorts = serialPorts;
    

    public string[] SerialPorts
    
        get
        
            return _serialPorts;
        
    

    public EventType EventType
    
        get
        
            return _eventType;
        
    

MonitorDeviceChanges 方法实际上可以查看所有设备更改（如设备管理器），但检查串行端口允许我们仅在更改时引发事件。

要使用代码，只需订阅PortsChanged 事件，例如SerialPortService.PortsChanged += (sender1, changedArgs) => DoSomethingSerial(changedArgs.SerialPorts);

哦，.Raise 方法只是我在某处找到的扩展方法：

/// <summary>
/// Tell subscribers, if any, that this event has been raised.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="handler">The generic event handler</param>
/// <param name="sender">this or null, usually</param>
/// <param name="args">Whatever you want sent</param>
public static void Raise<T>(this EventHandler<T> handler, object sender, T args) where T : EventArgs

    // Copy to temp var to be thread-safe (taken from C# 3.0 Cookbook - don't know if it's true)
    EventHandler<T> copy = handler;
    if (copy != null)
    
        copy(sender, args);
    

【讨论】：

您好，我尝试使用此代码，发现删除部分不是您能得到的最好的。当应用程序与设备连接并且您断开电缆时，您的代码会注意到这一点。但是，您看不到任何更改，因为程序尚未清理端口，GetPortNames 将返回不再可用的 comport。我只对删除事件感兴趣，所以我正在检查SerialPort 是否打开。如果端口关闭，则发生了移除事件。

@2pietjuh2 如果我理解你，你是对的。代码的重点不是检测串行端口的打开/关闭，而是检测是否向机器添加了新端口或之前的端口被删除。那么可能是您正在查看不同的问题吗？

您能解释一下事件类型 2 和 3 是什么以及存在哪些其他事件类型吗？

@JohnDemetriou 请参阅msdn.microsoft.com/en-us/library/windows/desktop/…，具体来说：配置已更改 (1) 设备到达 (2) 设备移除 (3) 对接 (4)

是否有人使用上述代码面临多个事件触发问题？

【参考方案4】：

您的设备更改事件可以与 WMI - PNP 实体一起使用。以下将返回设备详细信息 - 在下面的代码中显示设备名称。

Dim moReturn As Management.ManagementObjectCollection
Dim moSearch As Management.ManagementObjectSearcher
Dim mo As Management.ManagementObject
moSearch = New Management.ManagementObjectSearcher("Select * from Win32_PnPEntity")
moReturn = moSearch.Get

For Each mo In moReturn
If CStr(mo.Properties.Item("Name").Value).Contains("Prolific") Then
    returns something like: "Prolific USB-to-Serial Comm Port (COM17)"
    txtStatus.Text &= CStr(mo.Properties.Item("Name").Value) & vbCrLf
End If
Next

另请参阅代码以访问可用于过滤或监控更改的其他 PNP 属性：

On Error Resume Next
strComputer = "."
Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")
Set colItems = objWMIService.ExecQuery("Select * from Win32_PnPEntity",,48)
For Each objItem in colItems
    "Availability: " & objItem.Availability
    "Caption: " & objItem.Caption
    "ClassGuid: " & objItem.ClassGuid
    "ConfigManagerErrorCode: " & objItem.ConfigManagerErrorCode
    "ConfigManagerUserConfig: " & objItem.ConfigManagerUserConfig
    "CreationClassName: " & objItem.CreationClassName
    "Description: " & objItem.Description
    "DeviceID: " & objItem.DeviceID
    "ErrorCleared: " & objItem.ErrorCleared
    "ErrorDescription: " & objItem.ErrorDescription
    "InstallDate: " & objItem.InstallDate
    "LastErrorCode: " & objItem.LastErrorCode
    "Manufacturer: " & objItem.Manufacturer
    "Name: " & objItem.Name
    "PNPDeviceID: " & objItem.PNPDeviceID
    "PowerManagementCapabilities: " & objItem.PowerManagementCapabilities
    "PowerManagementSupported: " & objItem.PowerManagementSupported
    "Service: " & objItem.Service
    "Status: " & objItem.Status
    "StatusInfo: " & objItem.StatusInfo
    "SystemCreationClassName: " & objItem.SystemCreationClassName
    "SystemName: " & objItem.SystemName
Next

【参考方案5】：

注意：我试图将此作为对@Pat 答案的评论发布，但没有足够的声誉来做到这一点。

除了@2pietjuh2 的评论，RaisePortsChangedIfNecessary() 可以更改为以下内容：

private static void RaisePortsChangedIfNecessary(EventType eventType)

    lock (_serialPorts)
    
        var availableSerialPorts = GetAvailableSerialPorts();
        if (eventType == EventType.Insertion)
        
            var added = availableSerialPorts.Except(_serialPorts).ToArray();
            _serialPorts = availableSerialPorts;
            PortsChanged.Raise(null, new PortsChangedArgs(eventType, added));
        
        else if (eventType == EventType.Removal)
        
            var removed = _serialPorts.Except(availableSerialPorts).ToArray();
            _serialPorts = availableSerialPorts;
            PortsChanged.Raise(null, new PortsChangedArgs(eventType, removed));
        
    

然后引发的事件包括插入/移除的串行端口，而不是插入/移除后可用的串行端口列表。