检测串口插入/拔出 [英] Detect serial port insertion/removal
问题描述
我正在连接一个USB串行端口，该端口可以随时插入或卸下。我发现我可以使用 WMI （特别是使用 WMI代码创建器），以查询PC中的设备更改。
I am interfacing with a USB-to-serial port that can be inserted or removed at any time. I've found that I can use WMI (particularly with the use of WMI Code Creator) to query for device changes in the PC.
在下面的生成的代码段中， Win32_DeviceChangeEvent 已订阅。但是，此事件不会显示哪个设备（例如USB，串行端口等）引起了该事件。有没有一种方法只能在插入或卸下串行端口时接收通知？
In the generated snippet below, the Win32_DeviceChangeEvent is subscribed to. However, this event doesn't reveal which device (e.g. USB, serial port, etc) caused the event. Is there a way to only receive notifications when serial ports are inserted or removed?
要澄清一下，代码的重点是不来检测打开/关闭串行端口，来检测是否已将新端口添加到计算机中，或者是否已删除了先前的端口。
To clarify, the point of the code is not to detect opening/closing of serial ports, it is to detect whether a new port has been added to the machine or a previous port was removed.
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;
}
}
}
推荐答案
我最终使用WMI和@Hans的建议来检查哪些串行端口是新端口/丢失端口。
I ended up using WMI and @Hans' advice to check what serial ports are new/missing.
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 方法实际上可以看到所有设备更改（例如设备管理器），但是检查串行端口仅允许我们在更改后引发事件。
The MonitorDeviceChanges method actually sees all device changes (like Device Manager), but checking the serial ports allows us to only raise an event when those have changed.
要使用该代码，只需预订 PortsChanged 事件，例如 SerialPortService.PortsChanged + =（sender1，changedArgs）=> DoSomethingSerial（changedArgs.SerialPorts）;
To use the code, simply subscribe to the PortsChanged event, e.g. SerialPortService.PortsChanged += (sender1, changedArgs) => DoSomethingSerial(changedArgs.SerialPorts);
哦， .Raise 方法是只是我在某处选择的一种扩展方法：
Oh, and the .Raise method is just an extension method I picked up somewhere:
/// <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);
}
}
这篇关于检测串口插入/拔出的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
