连接或断开连接时检测 USB 到 RS232 转换器

Question

经过一番摸索，我设法在我的系统上找到了 USB 到 RS232 转换器的 com 端口号。我在当前系统中有 15 个。 我现在需要做的是检测一个连接或断开连接，以便我可以更新我的表。我可以弄清楚如何检测 USB 存储设备，但同样不适用于 USB 到 RS232 转换器。请问有谁知道我如何检测到这一点？

这是我用来计算转换器使用的 com 端口的代码 sn-p

private void btn_tst2_Click(object sender, EventArgs e)
{          
    ManagementObjectSearcher searcher = new ManagementObjectSearcher("root\\CIMV2",
    "SELECT * FROM Win32_PnPEntity WHERE ClassGuid=\"{4d36e978-e325-11ce-bfc1-08002be10318}\"");

    foreach (ManagementObject queryObj in searcher.Get())
    {
        rtxbx_output.AppendText(queryObj["Name"].ToString() +"\r");
    }

}

Answer 1

你可以做一些线程或任务来查询从方法System.IO.Ports.SerialPort.GetPortNames()返回的数组：当这个数组发生变化，或者添加了一个新元素时，就意味着一个新的串口已经连接到系统。

当然，它会返回您系统上的每个串口，但是您可以使用您的代码 sn-p 选择其中哪些是 USB-RS232 转换器。

Answer 2

你可以使用MSSerial_PortName请找sn-p。

注意：这不是一个有效的代码，您必须根据您的要求进行更改。

private void btn_tst2_Click(object sender, EventArgs e)
        {   
// connection to WMI rather than cimv2 namespace       
            ManagementObjectSearcher searcher = new ManagementObjectSearcher("root\\WMI",
            "select * from MSSerial_PortName");

            foreach (ManagementObject queryObj in searcher.Get())
            {
               queryObj["Active"]; // status
               queryObj["InstanceName"];  
               queryObj["PortName"]; // port number
            }

        }

Answer 3

在经历了很多挫折之后，我终于弄清楚了如何实现我所需要的。我发布答案，以防它指向将来困在同一区域的任何人。我在代码中包含了 cmets。我最后得到的是所有 Com 端口的列表，当一个人离开或加入时，它会刷新。在您的 PC 上可以找到文件 dbt.h。

要使下面的代码正常工作，只需使用富文本框和两个按钮制作一个解决方案。

    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Data;
    using System.Drawing;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;
    using System.Windows.Forms;
    using System.Management;    //used to perform WMI queries
    using System.Threading;
    using System.Runtime.InteropServices; // needed for marshalling

    namespace MissionControl
    {
        public partial class Control : Form
        {
            public Control()
            {
                InitializeComponent();
            }

            // WndProc = Window Procedures: Every window has an associated     window procedure — a function that processes all messages sent 
        // or posted to all windows of the class. All aspects of a window's appearance and behavior depend on the window procedure's 
        // response to these messages. see https://msdn.microsoft.com/en-us/library/ms632593%28v=vs.85%29.aspx
        protected override void WndProc(ref Message m)
        {
            //you may find these definitions in dbt.h 
            const int WM_DEVICECHANGE = 0x0219; // in dbt.h, BroadcastSpecialMessage constants. 
            const int DBT_DEVICEARRIVAL = 0x8000;  // system detected a device arrived see dbt.h
            const int DBT_DEVICEREMOVECOMPLETE = 0x8004; //system detected a device removal see dbt.h
            const int DBT_DEVTYP_PORT = 0x00000003;  // serial, parallel in dbt.h

            switch (m.Msg)
            {
                case WM_DEVICECHANGE:
                    switch (m.WParam.ToInt32())
                    {
                        case DBT_DEVICEARRIVAL:
                            {
                                // Get the DBT_DEVTYP* as defined in dbt.h
                                // We are looking for DBT_DEVTYP_PORT value = 3 which is Serial port
                                int devTypeA = Marshal.ReadInt32(m.LParam, 4);

                                if (devTypeA == DBT_DEVTYP_PORT)
                                {
                                    rchtxbx_output.SelectedText = string.Empty;
                                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                                    rchtxbx_output.SelectionColor = Color.Lime;
                                    rchtxbx_output.AppendText("\rSerial Port Connected\r\rList of Current Ports\r");

                                }
                                else
                                {
                                    // We should never get in here but just in case do somethign rather than fall over
                                    rchtxbx_output.SelectedText = string.Empty;
                                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                                    rchtxbx_output.SelectionColor = Color.Red;
                                    rchtxbx_output.AppendText("Non-Serial Port Connected\r");
                                }


                                //To prevent cross threading we will start the function call in its own thread
                                // Create the thread object, passing in GetPortNum
                                //ThreadA is the arrival thread (just connected)
                                Thread ThreadA = new Thread(new ThreadStart(GetPortNum));

                                // Start the thread via a ThreadStart delegate
                                ThreadA.Start();

                            }
                            break;
                        case DBT_DEVICEREMOVECOMPLETE:
                            {
                                // Get the DBT_DEVTYP* as defined in dbt.h
                                // We are looking for DBT_DEVTYP_PORT value = 3 which is Serial port
                                int devTypeD = Marshal.ReadInt32(m.LParam, 4);

                                if (devTypeD == DBT_DEVTYP_PORT)
                                {
                                    rchtxbx_output.SelectedText = string.Empty;
                                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                                    rchtxbx_output.SelectionColor = Color.Lime;
                                    rchtxbx_output.AppendText("\rSerial Port Disconnected\r\rList of Current Ports\r");
                                }
                                else
                                {
                                    // We should never get in here but just in case do something rather than fall over
                                    rchtxbx_output.SelectedText = string.Empty;
                                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                                    rchtxbx_output.SelectionColor = Color.Red;
                                    rchtxbx_output.AppendText("Non-Serial Port Disconneted\r");

                                }

                                //To prevent cross threading we will start the function call in its own thread
                                // Create the thread object, passing in GetPortNum
                                //ThreadD is the departure thread (disconnected) 
                                Thread ThreadD = new Thread(new ThreadStart(GetPortNum));

                                // Start the thread via a ThreadStart delegate
                                ThreadD.Start();
                            }

                            break;
                    }

                    break;
            }
            //we detect the media arrival event 
            base.WndProc(ref m);
        }


        private void btn_close_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void btn_clr_Click(object sender, EventArgs e)
        {
            rchtxbx_output.Clear();
        }

        private void GetPortNum()
        {
            //Windows Management Instrumentation (WMI) consists of a set of extensions to the Windows Driver Model that provides an 
            //operating system interface through which instrumented components provide information and notification. 
            // To work out the WMI to use, get the tool https://www.microsoft.com/en-us/download/details.aspx?id=8572

            //GUID (or UUID) is an acronym for 'Globally Unique Identifier' (or 'Universally Unique Identifier'). It is a 128-bit 
            //integer number used to identify resources. The term GUID is generally used by developers working with Microsoft 
            //technologies, while UUID is used everywhere else.
            // Get the list of ClassGUID from https://msdn.microsoft.com/en-us/library/windows/hardware/ff553426%28v=vs.85%29.aspx

            string comportnum = "";
            int textStart = 0;
            char[] textEnd = { ')' };


            ManagementObjectSearcher searcher = new ManagementObjectSearcher("root\\CIMV2",
                    "SELECT * FROM Win32_PnPEntity WHERE ClassGuid=\"{4d36e978-e325-11ce-bfc1-08002be10318}\"");
            foreach (ManagementObject queryObj in searcher.Get())
            {
                comportnum = queryObj["Name"].ToString(); // Get the name of the comm port

                //Format the string to extract the comport number only
                textStart = comportnum.IndexOf("(COM");
                comportnum = comportnum.Remove(0, textStart + 4).TrimEnd(textEnd);

                //To prevent cross threading use Invoke. We are writing to a control created in another thread.
                rchtxbx_output.Invoke(new EventHandler(delegate
                {
                    rchtxbx_output.SelectedText = string.Empty;
                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                    rchtxbx_output.SelectionColor = Color.Lime; //set font colour
                    rchtxbx_output.AppendText("Comm Port = " + comportnum + "\r"); //add some text
                    rchtxbx_output.ScrollToCaret(); // move cursor to the end
                }));
            }
        }
    }
}