How to open a serial port by friendly name?

Question

friendly name = the name that appears in "Device Manager" under "Ports (COM & LPT).

EDIT: two solutions provided below. One with WMI and another with SetupAPI.

Answer 1

If you are specifically using USB devices and not some other type of COM port, the cross-platform USB library libusbp has an example you can run that shows how to find the COM port name based on the USB product ID and vendor ID of the COM port.

That is a different but probably better choice than trying to use the friendly name in the Device Manager. Perhaps libusbp could be extended to allow access to the friendly name if you really want that.

Answer 2

I use virtual ports generated by com0com. With that you're able to name the ports as you want - so I've port captions like follows: "com0com - bus for serial port pair emulator 0 (COMA <-> COMB)"

With the above posted WMI code you will then get the name "COMA <-> COMB" for that port. It seems such constructs are no ports, but the above code will treat it as serial port...

BTW, "COMA" is a totally valid name for a port... (that means, looking for only numbers at the end is not enough).

So I wonder how I can reliably distinguish between a valid, existing serial port name and such strange constructs...

Answer 3

Pavel's class SetupDiWrap works great, it just needs a few small tweaks for Windows 7.

Hopefully, this update will help other people struggling (like me) to get COM port numbers from VCP names in Windows 7.

1) The SP_DEVINFO_DATA has changed in Windows 7, the total length is no longer 28 bytes, it is 32 bytes long. This is what works for me:

   private struct SP_DEVINFO_DATA
        {
            /// <summary>Size of the structure, in bytes.</summary>
            public int cbSize;
            /// <summary>GUID of the device interface class.</summary>
            public Guid ClassGuid;
            /// <summary>Handle to this device instance.</summary>
            public int DevInst;
            /// <summary>Reserved; do not use.</summary>
            public ulong Reserved;
        }

Note ulong for Reserved instead of an int. Changing uint cbSize to int cbSize saved me a cast later on, otherwise you can leave it as uint.

2) I also wrote the line:

 da.cbSize = (uint)Marshal.SizeOf(da);

a bit different, for clarity, to get the cbSize to 32 bits:

da.cbSize = Marshal.SizeOf(typeof(SP_DEVINFO_DATA));

3) I changed

 [DllImport("setupapi.dll", CharSet = CharSet.Auto)]
        static extern IntPtr SetupDiGetClassDevs(       
           ref Guid ClassGuid,
           IntPtr Enumerator,
           IntPtr hwndParent,
           int Flags
        );

to

 [DllImport("setupapi.dll", CharSet = CharSet.Auto)]
        private static extern IntPtr SetupDiGetClassDevs( 
           ref Guid ClassGuid,
           UInt32 Enumerator,
           IntPtr hwndParent,
           UInt32 Flags
        );

The Enumerator is no longer an IntPtr, so you need to call SetupDiGetClassDevs like this:

IntPtr h = SetupDiGetClassDevs(ref guidClone, 0, IntPtr.Zero, DIGCF_PRESENT | DIGCF_PROFILE);

Note "0" instead of IntPtr.Zero when passing the Enumerator.

The code now runs like a charm in Windows 7!

Answer 4

You might also want to consider using the registry as I have found WMI quite slow (5 or 6 seconds)

In my case I wanted to identify the COM port name of a device with a known friendly name. Using regedit i searched the registry for the friendly name in a key which also contained the COM port. Because the key I found was some sort of random ID along with 10 others I went up a few levels to find a key suitable to search within.

The code I came up with is as follows:

Dim searchFriendlyName = "Your Device Name".ToLower
Dim k0 = Registry.LocalMachine.OpenSubKey("SYSTEM\CurrentControlSet\Enum\USB\", False)
For Each k1Name In k0.GetSubKeyNames
    Dim k1 = k0.OpenSubKey(k1Name, False)
    For Each k2name In k1.GetSubKeyNames
        Dim k2 = k1.OpenSubKey(k2name, False)
        If k2.GetValueNames.Contains("FriendlyName") AndAlso k2.GetValue("FriendlyName").ToString.ToLower.Contains(searchFriendlyName) Then
            If k2.GetSubKeyNames.Contains("Device Parameters") Then
                Dim k3 = k2.OpenSubKey("Device Parameters", False)
                If k3.GetValueNames.Contains("PortName") Then
                    For Each s In SerialPort.GetPortNames
                        If k3.GetValue("PortName").ToString.ToLower = s.ToLower Then
                            Return s
                        End If
                    Next
                End If
            End If
        End If
    Next
Next

This will of course need to be modified depending upon how and where your device shows up in the registry but if you are trying to 'Auto Detect' the Com Port of a specific type of deivce then you should be able to make this work.

Remember if you have to recursivly search lots of keys then this will slow the above solution down so try and find the right place in the registry to look.

I also included WMI code after the registry search in case the registry search came up empty:

Dim mg As New System.Management.ManagementClass("Win32_SerialPort")
Try

    For Each i In mg.GetInstances()
        Dim name = i.GetPropertyValue("Name")
        If name IsNot Nothing AndAlso name.ToString.ToLower.Contains(searchFriendlyName.ToLower) Then
            Return i.GetPropertyValue("DeviceId").ToString
        End If
    Next
Finally
    mg.Dispose()
End Try

Answer 5

This article's code did the job for me (he links to this post, but doesn't seem to have provided an answer here himself). Here's the author's code:

using System.Management;
internal class ProcessConnection { 

   public static ConnectionOptions ProcessConnectionOptions()
   {
     ConnectionOptions options = new ConnectionOptions();
     options.Impersonation = ImpersonationLevel.Impersonate;
     options.Authentication = AuthenticationLevel.Default;
     options.EnablePrivileges = true;
     return options;
   }

   public static ManagementScope ConnectionScope(string machineName, ConnectionOptions options, string path)
   {
     ManagementScope connectScope = new ManagementScope();
     connectScope.Path = new ManagementPath(@"\\" + machineName + path);
     connectScope.Options = options;
     connectScope.Connect();
     return connectScope;
   }
}

public class COMPortInfo
{
   public string Name { get; set; }
   public string Description { get; set; }

   public COMPortInfo() { }     

   public static List<COMPortInfo> GetCOMPortsInfo()
   {
     List<COMPortInfo> comPortInfoList = new List<COMPortInfo>();

     ConnectionOptions options = ProcessConnection.ProcessConnectionOptions();
     ManagementScope connectionScope = ProcessConnection.ConnectionScope(Environment.MachineName, options, @"\root\CIMV2");

     ObjectQuery objectQuery = new ObjectQuery("SELECT * FROM Win32_PnPEntity WHERE ConfigManagerErrorCode = 0");
     ManagementObjectSearcher comPortSearcher = new ManagementObjectSearcher(connectionScope, objectQuery);

     using (comPortSearcher)
     {
       string caption = null;
       foreach (ManagementObject obj in comPortSearcher.Get())
       {
         if (obj != null)
         {
           object captionObj = obj["Caption"];
           if (captionObj != null)
           {
              caption = captionObj.ToString();
              if (caption.Contains("(COM"))
              {
                COMPortInfo comPortInfo = new COMPortInfo();
                comPortInfo.Name = caption.Substring(caption.LastIndexOf("(COM")).Replace("(", string.Empty).Replace(")",
                                                     string.Empty);
                comPortInfo.Description = caption;
                comPortInfoList.Add(comPortInfo);
              }
           }
         }
       }
     } 
     return comPortInfoList;
   } 
}

Usage:

foreach (COMPortInfo comPort in COMPortInfo.GetCOMPortsInfo())
{
  Console.WriteLine(string.Format("{0} – {1}", comPort.Name, comPort.Description));
}

Answer 6

I know this was posted in C#, but I am certain this can easily be converted...

    Public Function foo() As Integer
    Try
        Dim searcher As New ManagementObjectSearcher( _
            "root\CIMV2", _
            "SELECT * FROM Win32_SerialPort")

        For Each queryObj As ManagementObject In searcher.Get()
            Debug.WriteLine(queryObj("Caption"))
            Debug.WriteLine(queryObj("Description"))
            Debug.WriteLine(queryObj("DeviceID"))
            Debug.WriteLine(queryObj("Name"))
            Debug.WriteLine(queryObj("PNPDeviceID"))

        Next
    Catch err As ManagementException
        Stop
    End Try
End Function

Public Function bar() As Integer
    Try
        Dim searcher As New ManagementObjectSearcher( _
            "root\CIMV2", _
            "SELECT * FROM Win32_PnPEntity WHERE ConfigManagerErrorCode = 0")

        For Each queryObj As ManagementObject In searcher.Get()
            If queryObj("Caption").ToString.Contains("(COM") Then
                Debug.WriteLine(queryObj("Caption"))
                Debug.WriteLine(queryObj("Description"))
                Debug.WriteLine(queryObj("DeviceID"))
                Debug.WriteLine(queryObj("Name"))
                Debug.WriteLine(queryObj("PNPDeviceID"))
            End If
        Next
    Catch err As ManagementException
        Stop
    End Try
End Function

It finds all of my com ports, modem, serial, usb, and bluetooth.

Answer 7

Try running a WMI query on the Win32_SerialPort class. Download WmiCodeCreator to experiment and auto-generate the C# code.

Answer 8

Posting tonight's code, for everybody's enjoyment:

public class SetupDiWrap
{
    static public string ComPortNameFromFriendlyNamePrefix(string friendlyNamePrefix)
    {
        const string className = "Ports";
        Guid[] guids = GetClassGUIDs(className);

        System.Text.RegularExpressions.Regex friendlyNameToComPort =
            new System.Text.RegularExpressions.Regex(@".? \((COM\d+)\)$");  // "..... (COMxxx)" -> COMxxxx

        foreach (Guid guid in guids)
        {
            // We start at the "root" of the device tree and look for all
            // devices that match the interface GUID of a disk
            Guid guidClone = guid;
            IntPtr h = SetupDiGetClassDevs(ref guidClone, IntPtr.Zero, IntPtr.Zero, DIGCF_PRESENT | DIGCF_PROFILE);
            if (h.ToInt32() != INVALID_HANDLE_VALUE)
            {
                int nDevice = 0;
                while (true)
                {
                    SP_DEVINFO_DATA da = new SP_DEVINFO_DATA();
                    da.cbSize = (uint)Marshal.SizeOf(da);

                    if (0 == SetupDiEnumDeviceInfo(h, nDevice++, ref da))
                        break;

                    uint RegType;
                    byte[] ptrBuf = new byte[BUFFER_SIZE];
                    uint RequiredSize;
                    if (SetupDiGetDeviceRegistryProperty(h, ref da,
                        (uint)SPDRP.FRIENDLYNAME, out RegType, ptrBuf,
                        BUFFER_SIZE, out RequiredSize))
                    {
                        const int utf16terminatorSize_bytes = 2;
                        string friendlyName = System.Text.UnicodeEncoding.Unicode.GetString(ptrBuf, 0, (int)RequiredSize - utf16terminatorSize_bytes);

                        if (!friendlyName.StartsWith(friendlyNamePrefix))
                            continue;

                        if (!friendlyNameToComPort.IsMatch(friendlyName))
                            continue;

                        return friendlyNameToComPort.Match(friendlyName).Groups[1].Value;
                    }
                } // devices
                SetupDiDestroyDeviceInfoList(h);
            }
        } // class guids

        return null;
    }

    /// <summary>
    /// The SP_DEVINFO_DATA structure defines a device instance that is a member of a device information set.
    /// </summary>
    [StructLayout(LayoutKind.Sequential)]
    private struct SP_DEVINFO_DATA
    {
        /// <summary>Size of the structure, in bytes.</summary>
        public uint cbSize;
        /// <summary>GUID of the device interface class.</summary>
        public Guid ClassGuid;
        /// <summary>Handle to this device instance.</summary>
        public uint DevInst;
        /// <summary>Reserved; do not use.</summary>
        public uint Reserved;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct SP_DEVICE_INTERFACE_DATA
    {
        public Int32 cbSize;
        public Guid interfaceClassGuid;
        public Int32 flags;
        private UIntPtr reserved;
    }

    const int BUFFER_SIZE = 1024;

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    private struct SP_DEVICE_INTERFACE_DETAIL_DATA
    {
        public int cbSize;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = BUFFER_SIZE)]
        public string DevicePath;
    }

    private enum SPDRP
    {
        DEVICEDESC = 0x00000000,
        HARDWAREID = 0x00000001,
        COMPATIBLEIDS = 0x00000002,
        NTDEVICEPATHS = 0x00000003,
        SERVICE = 0x00000004,
        CONFIGURATION = 0x00000005,
        CONFIGURATIONVECTOR = 0x00000006,
        CLASS = 0x00000007,
        CLASSGUID = 0x00000008,
        DRIVER = 0x00000009,
        CONFIGFLAGS = 0x0000000A,
        MFG = 0x0000000B,
        FRIENDLYNAME = 0x0000000C,
        LOCATION_INFORMATION = 0x0000000D,
        PHYSICAL_DEVICE_OBJECT_NAME = 0x0000000E,
        CAPABILITIES = 0x0000000F,
        UI_NUMBER = 0x00000010,
        UPPERFILTERS = 0x00000011,
        LOWERFILTERS = 0x00000012,
        MAXIMUM_PROPERTY = 0x00000013,
    }

    [DllImport("setupapi.dll", SetLastError = true)]
    static extern bool SetupDiClassGuidsFromName(string ClassName,
        ref Guid ClassGuidArray1stItem, UInt32 ClassGuidArraySize,
        out UInt32 RequiredSize);

    [DllImport("setupapi.dll")]
    internal static extern IntPtr SetupDiGetClassDevsEx(IntPtr ClassGuid,
        [MarshalAs(UnmanagedType.LPStr)]String enumerator,
        IntPtr hwndParent, Int32 Flags, IntPtr DeviceInfoSet,
        [MarshalAs(UnmanagedType.LPStr)]String MachineName, IntPtr Reserved);

    [DllImport("setupapi.dll")]
    internal static extern Int32 SetupDiDestroyDeviceInfoList(IntPtr DeviceInfoSet);

    [DllImport(@"setupapi.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern Boolean SetupDiEnumDeviceInterfaces(
       IntPtr hDevInfo,
       IntPtr optionalCrap, //ref SP_DEVINFO_DATA devInfo,
       ref Guid interfaceClassGuid,
       UInt32 memberIndex,
       ref SP_DEVICE_INTERFACE_DATA deviceInterfaceData
    );

    [DllImport("setupapi.dll")]
    private static extern Int32 SetupDiEnumDeviceInfo(IntPtr DeviceInfoSet,
        Int32 MemberIndex, ref SP_DEVINFO_DATA DeviceInterfaceData);

    [DllImport("setupapi.dll")]
    private static extern Int32 SetupDiClassNameFromGuid(ref Guid ClassGuid,
        StringBuilder className, Int32 ClassNameSize, ref Int32 RequiredSize);

    [DllImport("setupapi.dll")]
    private static extern Int32 SetupDiGetClassDescription(ref Guid ClassGuid,
        StringBuilder classDescription, Int32 ClassDescriptionSize, ref Int32 RequiredSize);

    [DllImport("setupapi.dll")]
    private static extern Int32 SetupDiGetDeviceInstanceId(IntPtr DeviceInfoSet,
        ref SP_DEVINFO_DATA DeviceInfoData,
        StringBuilder DeviceInstanceId, Int32 DeviceInstanceIdSize, ref Int32 RequiredSize);

    [DllImport("setupapi.dll", CharSet = CharSet.Auto)]
    static extern IntPtr SetupDiGetClassDevs(           // 1st form using a ClassGUID only, with null Enumerator
       ref Guid ClassGuid,
       IntPtr Enumerator,
       IntPtr hwndParent,
       int Flags
    );

    [DllImport(@"setupapi.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern Boolean SetupDiGetDeviceInterfaceDetail(
       IntPtr hDevInfo,
       ref SP_DEVICE_INTERFACE_DATA deviceInterfaceData,
       ref SP_DEVICE_INTERFACE_DETAIL_DATA deviceInterfaceDetailData,
       UInt32 deviceInterfaceDetailDataSize,
       out UInt32 requiredSize,
       ref SP_DEVINFO_DATA deviceInfoData
    );

    /// <summary>
    /// The SetupDiGetDeviceRegistryProperty function retrieves the specified device property.
    /// This handle is typically returned by the SetupDiGetClassDevs or SetupDiGetClassDevsEx function.
    /// </summary>
    /// <param Name="DeviceInfoSet">Handle to the device information set that contains the interface and its underlying device.</param>
    /// <param Name="DeviceInfoData">Pointer to an SP_DEVINFO_DATA structure that defines the device instance.</param>
    /// <param Name="Property">Device property to be retrieved. SEE MSDN</param>
    /// <param Name="PropertyRegDataType">Pointer to a variable that receives the registry data Type. This parameter can be NULL.</param>
    /// <param Name="PropertyBuffer">Pointer to a buffer that receives the requested device property.</param>
    /// <param Name="PropertyBufferSize">Size of the buffer, in bytes.</param>
    /// <param Name="RequiredSize">Pointer to a variable that receives the required buffer size, in bytes. This parameter can be NULL.</param>
    /// <returns>If the function succeeds, the return value is nonzero.</returns>
    [DllImport("setupapi.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern bool SetupDiGetDeviceRegistryProperty(
        IntPtr DeviceInfoSet,
        ref SP_DEVINFO_DATA DeviceInfoData,
        uint Property,
        out UInt32 PropertyRegDataType,
        byte[] PropertyBuffer,
        uint PropertyBufferSize,
        out UInt32 RequiredSize);


    const int DIGCF_DEFAULT = 0x1;
    const int DIGCF_PRESENT = 0x2;
    const int DIGCF_ALLCLASSES = 0x4;
    const int DIGCF_PROFILE = 0x8;
    const int DIGCF_DEVICEINTERFACE = 0x10;
    const int INVALID_HANDLE_VALUE = -1;

    private static Guid[] GetClassGUIDs(string className)
    {
        UInt32 requiredSize = 0;
        Guid[] guidArray = new Guid[1];

        bool status = SetupDiClassGuidsFromName(className, ref guidArray[0], 1, out requiredSize);
        if (true == status)
        {
            if (1 < requiredSize)
            {
                guidArray = new Guid[requiredSize];
                SetupDiClassGuidsFromName(className, ref guidArray[0], requiredSize, out requiredSize);
            }
        }
        else
            throw new System.ComponentModel.Win32Exception();

        return guidArray;
    }


}