According to this stack overflow thread, PJ Naughter has implemented 9 methods to emunerate com port in Windows. That code was namedEnumSerialPorts.





     As my using, I found some method would list non-existed com ports. for example:



My computer com port be :

But the output of  PJ Naughte's EnumSerialPorts be :

CreateFile method reports

COM1

COM4

COM5

COM98

COM99

QueryDosDevice method reports

COM5

COM1

COM98

COM99

COM4

GetDefaultCommConfig method reports

COM1

COM4

COM5

COM98

COM99

Device Manager (SetupAPI - GUID_DEVINTERFACE_COMPORT) reports

COM1 <通訊連接埠>

COM4 <USB Serial Port>

Device Manager (SetupAPI - Ports Device information set) reports

COM99 <Bluetooth Serial Port>

COM4 <USB Serial Port>

COM1 <通訊連接埠>

COM98 <Bluetooth Serial Port>

COM5 <USB-SERIAL CH340>

EnumPorts method reports

COM1

COM2

COM4

COM7

COM8

COM10

COM6

COM5

COM98

COM99

COM9

COM11

COM12

COM13

COM14

COM16

COM17

COM18

COM19

COM20

COM21

COM22

COM23

COM24

COM25

COM26

COM27

COM28

COM29

COM30

COM31

COM32

COM3

WMI method reports

COM1 <通訊連接埠 (COM1)>

ComDB method reports

COM1

COM3

COM4

COM5

COM6

COM7

COM8

COM9

COM22

COM23

COM24

COM25

COM26

COM27

COM28

COM29

COM30

COM31

COM32

COM98

COM99

Registry method reports

COM98

COM99

COM5

COM1

COM4

Otherwise, that code are too extrvagen, those is hard to separate into an individual function: it is too much dependency on the other functions.



I has reorganized those functions being independent forms in C(instead of C++), those are more portable and useful. I also eliminated some methods which would report unused com ports.



My code be :

/*

 Enumerating com ports in Windows 

 original by PJ Naughter, 1998 - 2013

 http://www.naughter.com/enumser.html  (Web: www.naughter.com, Email: pjna@naughter.com)

 reorganize by Gaiger Chen , Jul, 2015

 NO COPYRIGHT,  welcome to use for everyone.

*/

#include <windows.h>

#include <stdio.h>

#include <tchar.h>

#include <setupapi.h>

#include <locale.h>

#define MAX_PORT_NUM      (256)

#define MAX_STR_LEN       (256*sizeof(TCHAR))

/*assure portName be double ARRAY , not double point*/

BOOL EnumerateComPortByCreateFile(UINT *pNumber, TCHAR *pPortName, int strMaxLen)

{

 UINT i, jj;

 INT ret;

 TCHAR *pTempPortName; 

 *pNumber = 0;

 jj = 0;

 pTempPortName = (TCHAR*)HeapAlloc(GetProcessHeap(),

    HEAP_GENERATE_EXCEPTIONS|HEAP_ZERO_MEMORY,

    strMaxLen*sizeof(pTempPortName));

 ret = FALSE;

 for (i = 1; i<= 255; i++){

  HANDLE hSerial;

  _stprintf_s(pTempPortName, strMaxLen, TEXT("\\\\.\\COM%u"), i);

  hSerial = CreateFile(pTempPortName, GENERIC_READ | GENERIC_WRITE,

   0, 0, OPEN_EXISTING, 0, 0);

  if(INVALID_HANDLE_VALUE == hSerial)

   continue;

  _tcsncpy(pPortName + jj*strMaxLen, pTempPortName,

   _tcsnlen(pTempPortName, strMaxLen));

  jj++;

 }/*for [i MAX_PORT_NUM] */

 HeapFree(GetProcessHeap(), 0, pTempPortName); pTempPortName = NULL;

 *pNumber = jj;

 if(0 <jj)

  ret = TRUE;

 return ret;

}/*EnumerateComPortByCreateFile*/

BOOL EnumerateComPortQueryDosDevice(UINT *pNumber, TCHAR *pPortName, int strMaxLen)

{

 UINT i, jj;

 INT ret;

 OSVERSIONINFOEX osvi;

 ULONGLONG dwlConditionMask;

 DWORD dwChars;

 TCHAR *pDevices;

 UINT nChars;

 ret = FALSE;

 memset(&osvi, 0, sizeof(osvi));

 osvi.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);

 osvi.dwPlatformId = VER_PLATFORM_WIN32_NT;

 dwlConditionMask = 0;

 VER_SET_CONDITION(dwlConditionMask, VER_PLATFORMID, VER_EQUAL);

 if(FALSE == VerifyVersionInfo(&osvi, VER_PLATFORMID, dwlConditionMask))

 {

   DWORD dwError = GetLastError();

  _tprintf(TEXT("VerifyVersionInfo error, %d\n", dwError));

  return -1;

 }/*if*/

 pDevices = NULL;

 nChars = 4096;

 pDevices = (TCHAR*)HeapAlloc(GetProcessHeap(),

  HEAP_GENERATE_EXCEPTIONS, nChars*sizeof(TCHAR));

 while(0 < nChars)

 {

  dwChars = QueryDosDevice(NULL, pDevices, nChars);

  if(0 == dwChars)

  {

   DWORD dwError = GetLastError();

   if(ERROR_INSUFFICIENT_BUFFER == dwError)

   {

    nChars *= 2;

    HeapFree(GetProcessHeap(), 0, pDevices);

    pDevices = (TCHAR*)HeapAlloc(GetProcessHeap(),

     HEAP_GENERATE_EXCEPTIONS, nChars*sizeof(TCHAR));

    continue;

   }/*if ERROR_INSUFFICIENT_BUFFER == dwError*/

   _tprintf(TEXT("QueryDosDevice error, %d\n", dwError));

   return -1;

  }/*if */

  //printf("dwChars = %d\n", dwChars);

  i = 0;

  jj = 0;

  while (TEXT('\0') != pDevices[i] )

  {

   TCHAR* pszCurrentDevice;

   size_t nLen;

   pszCurrentDevice = &(pDevices[i]);

   nLen = _tcslen(pszCurrentDevice);

   //_tprintf(TEXT("%s\n"), &pTargetPathStr[i]);

   if (3 < nLen)

            {

              if ((0 == _tcsnicmp(pszCurrentDevice, TEXT("COM"), 3))

      && FALSE != isdigit(pszCurrentDevice[3]) )

              {

                //Work out the port number

    _tcsncpy(pPortName + jj*strMaxLen,

     pszCurrentDevice, MAX_STR_LEN);

    jj++; 

              }

            }

   i += (nLen + 1);

  }

  break;

 }/*while*/

 if(NULL != pDevices)

  HeapFree(GetProcessHeap(), 0, pDevices); 

 *pNumber = jj;

 if(0 < jj)

  ret = TRUE;

 return ret;

}/*EnumerateComPortByQueryDosDevice*/

BOOL EnumerateComPortByGetDefaultCommConfig(UINT *pNumber, TCHAR *pPortName,

  int strMaxLen)

{

 UINT i, jj;

 INT ret;

 TCHAR *pTempPortName; 

 pTempPortName = (TCHAR*)HeapAlloc(GetProcessHeap(),

  HEAP_GENERATE_EXCEPTIONS| HEAP_ZERO_MEMORY, strMaxLen);

 *pNumber = 0;

 jj = 0;

 ret = FALSE;

 for (i = 1; i<=255; i++){    

  //Form the Raw device name

  COMMCONFIG cc;

  DWORD dwSize ;

  dwSize = sizeof(COMMCONFIG);

  _stprintf_s(pTempPortName, strMaxLen/2, TEXT("COM%u"), i);

  if (FALSE == GetDefaultCommConfig(pTempPortName, &cc, &dwSize))

    continue;

  _tcsncpy(pPortName + jj*strMaxLen, pTempPortName,

   _tcsnlen(pTempPortName, strMaxLen));

  jj++;

 }/*for [1 255] */

 HeapFree(GetProcessHeap(), 0, pTempPortName);

  pTempPortName = NULL;

 *pNumber = jj;

 if(0 <jj)

  ret = TRUE;

 return ret;

}/*EnumerateComPortByGetDefaultCommConfig*/

BOOL EnumerateComPortSetupAPI_GUID_DEVINTERFACE_COMPORT(UINT *pNumber,

   TCHAR *pPortName, int strMaxLen, TCHAR *pFriendName)

{

 UINT i, jj;

 INT ret;

 TCHAR *pTempPortName;

 HMODULE hLibrary;

 TCHAR szFullPath[_MAX_PATH];

 GUID guid;

 HDEVINFO hDevInfoSet;

 typedef HKEY (__stdcall SetupDiOpenDevRegKeyFunType)

  (HDEVINFO, PSP_DEVINFO_DATA, DWORD, DWORD, DWORD, REGSAM);

 //typedef BOOL (__stdcall SetupDiClassGuidsFromNameFunType)

 // (LPCTSTR, LPGUID, DWORD, PDWORD);

 typedef BOOL (__stdcall SetupDiDestroyDeviceInfoListFunType)

  (HDEVINFO);

 typedef BOOL (__stdcall SetupDiEnumDeviceInfoFunType)

  (HDEVINFO, DWORD, PSP_DEVINFO_DATA);

 typedef HDEVINFO (__stdcall SetupDiGetClassDevsFunType)

  (LPGUID, LPCTSTR, HWND, DWORD);

 typedef BOOL (__stdcall SetupDiGetDeviceRegistryPropertyFunType)

  (HDEVINFO, PSP_DEVINFO_DATA, DWORD, PDWORD, PBYTE, DWORD, PDWORD);

 SetupDiOpenDevRegKeyFunType* SetupDiOpenDevRegKeyFunPtr;

 SetupDiGetClassDevsFunType *SetupDiGetClassDevsFunPtr;

 SetupDiGetDeviceRegistryPropertyFunType *SetupDiGetDeviceRegistryPropertyFunPtr;

 SetupDiDestroyDeviceInfoListFunType *SetupDiDestroyDeviceInfoListFunPtr;

 SetupDiEnumDeviceInfoFunType *SetupDiEnumDeviceInfoFunPtr; 

 BOOL bMoreItems;

 SP_DEVINFO_DATA devInfo;

 ret = FALSE;

 jj = 0;

 szFullPath[0] = _T('\0'); 

 //Get the Windows System32 directory

 if(0 == GetSystemDirectory(szFullPath, _countof(szFullPath)))

 {

  _tprintf(TEXT("CEnumerateSerial::UsingSetupAPI1 failed, Error:%u\n"),

   GetLastError());

  return FALSE;

 }/*if*/

 //Setup the full path and delegate to LoadLibrary

#pragma warning(suppress: 6102) //There is a bug with the SAL annotation of GetSystemDirectory in the Windows 8.1 SDK

 _tcscat_s(szFullPath, _countof(szFullPath), _T("\\"));

 _tcscat_s(szFullPath, _countof(szFullPath), TEXT("SETUPAPI.DLL"));

 hLibrary = LoadLibrary(szFullPath);

 SetupDiOpenDevRegKeyFunPtr =

  (SetupDiOpenDevRegKeyFunType*)GetProcAddress(hLibrary, "SetupDiOpenDevRegKey");

#if defined _UNICODE

 SetupDiGetClassDevsFunPtr =

  (SetupDiGetClassDevsFunType*)GetProcAddress(hLibrary, "SetupDiGetClassDevsW");

 SetupDiGetDeviceRegistryPropertyFunPtr = (SetupDiGetDeviceRegistryPropertyFunType*)

  GetProcAddress(hLibrary, "SetupDiGetDeviceRegistryPropertyW");

#else

 SetupDiGetClassDevsFunPtr =

  (SetupDiGetClassDevsFunType*)GetProcAddress(hLibrary, "SetupDiGetClassDevsA");

 SetupDiGetDeviceRegistryPropertyFunPtr = (SetupDiGetDeviceRegistryPropertyFunType*)

  GetProcAddress(hLibrary, "SetupDiGetDeviceRegistryPropertyA");

#endif

  SetupDiDestroyDeviceInfoListFunPtr = (SetupDiDestroyDeviceInfoListFunType*)

  GetProcAddress(hLibrary, "SetupDiDestroyDeviceInfoList");

 SetupDiEnumDeviceInfoFunPtr = (SetupDiEnumDeviceInfoFunType*)

  GetProcAddress(hLibrary, "SetupDiEnumDeviceInfo");

 guid = GUID_DEVINTERFACE_COMPORT;

 hDevInfoSet = SetupDiGetClassDevsFunPtr(&guid, NULL, NULL,

  DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);

 if (INVALID_HANDLE_VALUE == hDevInfoSet)

 {

  //Set the error to report

  _tprintf(TEXT("error lpfnSETUPDIGETCLASSDEVS, %d"), GetLastError());

  return FALSE;

 }/*if */

 //bMoreItems = TRUE;

 devInfo.cbSize = sizeof(SP_DEVINFO_DATA);

 i = 0;

 jj = 0;

 do

 {

  HKEY hDeviceKey;

  BOOL isFound;

  isFound = FALSE;

  bMoreItems = SetupDiEnumDeviceInfoFunPtr(hDevInfoSet, i, &devInfo); 

  if(FALSE == bMoreItems)

   break;   

  i++;

  hDeviceKey = SetupDiOpenDevRegKeyFunPtr(hDevInfoSet, &devInfo,

   DICS_FLAG_GLOBAL, 0, DIREG_DEV, KEY_QUERY_VALUE);

  if (INVALID_HANDLE_VALUE != hDeviceKey)

  {

   int nPort;

   size_t nLen;

   LPTSTR pszPortName;

   nPort = 0;

   pszPortName = NULL;

   {

    //First query for the size of the registry value

    DWORD dwType;

    DWORD dwDataSize;

    LONG err;

    DWORD dwAllocatedSize;

    DWORD dwReturnedSize;

    dwType = 0; dwDataSize = 0; 

    err = RegQueryValueEx(hDeviceKey, TEXT("PortName"), NULL,

     &dwType, NULL, &dwDataSize);

    if (ERROR_SUCCESS != err)

     continue;    

    //Ensure the value is a string

    if (dwType != REG_SZ)

     continue;

    //Allocate enough bytes for the return value

    dwAllocatedSize = dwDataSize + sizeof(TCHAR);

    /* +sizeof(TCHAR) is to allow us to NULL terminate

     the data if it is not null terminated in the registry

    */

    pszPortName = (LPTSTR)LocalAlloc(LMEM_FIXED, dwAllocatedSize); 

    if (pszPortName == NULL)

     continue;

    //Recall RegQueryValueEx to return the data

    pszPortName[0] = _T('\0');

    dwReturnedSize = dwAllocatedSize;

    err = RegQueryValueEx(hDeviceKey, TEXT("PortName"), NULL,

     &dwType, (LPBYTE)pszPortName, &dwReturnedSize);

    if (ERROR_SUCCESS != err)

    {

     LocalFree(pszPortName);

     pszPortName = NULL;

     continue;

    }

    //Handle the case where the data just returned is the same size as the allocated size. This could occur where the data

    //has been updated in the registry with a non null terminator between the two calls to ReqQueryValueEx above. Rather than

    //return a potentially non-null terminated block of data, just fail the method call

    if (dwReturnedSize >= dwAllocatedSize)

     continue;        

    //NULL terminate the data if it was not returned NULL terminated because it is not stored null terminated in the registry

    if (pszPortName[dwReturnedSize/sizeof(TCHAR) - 1] != _T('\0'))

     pszPortName[dwReturnedSize/sizeof(TCHAR)] = _T('\0');

   }/*local varable*/

   //If it looks like "COMX" then

   //add it to the array which will be returned

   nLen = _tcslen(pszPortName);

   if (3 < nLen)

   {

     if (0 == _tcsnicmp(pszPortName, TEXT("COM"), 3))

     {

     if(FALSE == isdigit(pszPortName[3]) )

      continue;

    //Work out the port number

     _tcsncpy(pPortName + jj*strMaxLen, pszPortName,

     _tcsnlen(pszPortName, strMaxLen));

    //_stprintf_s(&portName[jj][0], strMaxLen, TEXT("%s"), pszPortName);

     } else

     {

      continue;

     }/*if 0 == _tcsnicmp(pszPortName, TEXT("COM"), 3)*/

   }/*if 3 < nLen*/

   LocalFree(pszPortName);

   isFound = TRUE;   

   //Close the key now that we are finished with it

   RegCloseKey(hDeviceKey);

  }/*INVALID_HANDLE_VALUE != hDeviceKey*/

  if(FALSE == isFound)

   continue;

  //If the port was a serial port, then also try to get its friendly name

  {

   TCHAR szFriendlyName[1024];

   DWORD dwSize;

   DWORD dwType;

   szFriendlyName[0] = _T('\0');

   dwSize = sizeof(szFriendlyName);

   dwType = 0;

   if( (TRUE == SetupDiGetDeviceRegistryPropertyFunPtr(hDevInfoSet, &devInfo,

       SPDRP_DEVICEDESC, &dwType, (PBYTE)(szFriendlyName),

       dwSize, &dwSize) ) && (REG_SZ == dwType)

   )

   {

    _tcsncpy(pFriendName + jj*strMaxLen, &szFriendlyName[0],

     _tcsnlen(&szFriendlyName[0], strMaxLen));

   }

   else

   {

    _stprintf_s(pFriendName + jj*strMaxLen, strMaxLen, TEXT(""));

   }/*if SetupDiGetDeviceRegistryPropertyFunPtr */

  }/*local variable */

  jj++;

 }while(1);

 *pNumber = jj;

 if(0 <jj)

  ret = TRUE;

 return ret;

}/*EnumerateComPortSetupAPI_GUID_DEVINTERFACE_COMPORT*/

BOOL EnumerateComPortSetupAPISetupDiClassGuidsFromNamePort(UINT *pNumber,

  TCHAR *pPortName, int strMaxLen, TCHAR *pFriendName)

{

 UINT i, jj;

 INT ret;

 TCHAR *pTempPortName;

 HMODULE hLibrary;

 TCHAR szFullPath[_MAX_PATH];

 GUID *pGuid;

 DWORD dwGuids;

 HDEVINFO hDevInfoSet;

 typedef HKEY (__stdcall SetupDiOpenDevRegKeyFunType)

  (HDEVINFO, PSP_DEVINFO_DATA, DWORD, DWORD, DWORD, REGSAM);

 typedef BOOL (__stdcall SetupDiClassGuidsFromNameFunType)

  (LPCTSTR, LPGUID, DWORD, PDWORD);

 typedef BOOL (__stdcall SetupDiDestroyDeviceInfoListFunType)

  (HDEVINFO);

 typedef BOOL (__stdcall SetupDiEnumDeviceInfoFunType)

  (HDEVINFO, DWORD, PSP_DEVINFO_DATA);

 typedef HDEVINFO (__stdcall SetupDiGetClassDevsFunType)

  (LPGUID, LPCTSTR, HWND, DWORD);

 typedef BOOL (__stdcall SetupDiGetDeviceRegistryPropertyFunType)

  (HDEVINFO, PSP_DEVINFO_DATA, DWORD, PDWORD, PBYTE, DWORD, PDWORD);

 SetupDiOpenDevRegKeyFunType* SetupDiOpenDevRegKeyFunPtr;

 SetupDiClassGuidsFromNameFunType *SetupDiClassGuidsFromNameFunPtr;

 SetupDiGetClassDevsFunType *SetupDiGetClassDevsFunPtr;

 SetupDiGetDeviceRegistryPropertyFunType *SetupDiGetDeviceRegistryPropertyFunPtr; 

 SetupDiDestroyDeviceInfoListFunType *SetupDiDestroyDeviceInfoListFunPtr;

 SetupDiEnumDeviceInfoFunType *SetupDiEnumDeviceInfoFunPtr; 

 BOOL bMoreItems;

 SP_DEVINFO_DATA devInfo;

 ret = FALSE;

 jj = 0;

 szFullPath[0] = _T('\0'); 

 //Get the Windows System32 directory

 if(0 == GetSystemDirectory(szFullPath, _countof(szFullPath)))

 {

  _tprintf(TEXT("CEnumerateSerial::UsingSetupAPI1 failed, Error:%u\n"),

   GetLastError());

  return FALSE;

 }/*if*/

 //Setup the full path and delegate to LoadLibrary

#pragma warning(suppress: 6102) //There is a bug with the SAL annotation of GetSystemDirectory in the Windows 8.1 SDK

 _tcscat_s(szFullPath, _countof(szFullPath), _T("\\"));

 _tcscat_s(szFullPath, _countof(szFullPath), TEXT("SETUPAPI.DLL"));

 hLibrary = LoadLibrary(szFullPath);

 SetupDiOpenDevRegKeyFunPtr =

  (SetupDiOpenDevRegKeyFunType*)GetProcAddress(hLibrary, "SetupDiOpenDevRegKey");

#if defined _UNICODE

 SetupDiClassGuidsFromNameFunPtr = (SetupDiClassGuidsFromNameFunType*)

  GetProcAddress(hLibrary, "SetupDiGetDeviceRegistryPropertyW");

 SetupDiGetClassDevsFunPtr =

  (SetupDiGetClassDevsFunType*)GetProcAddress(hLibrary, "SetupDiGetClassDevsW");

 SetupDiGetDeviceRegistryPropertyFunPtr

  = (SetupDiGetDeviceRegistryPropertyFunType*)GetProcAddress(hLibrary, "SetupDiGetDeviceRegistryPropertyW");

#else

 SetupDiClassGuidsFromNameFunPtr = (SetupDiClassGuidsFromNameFunType*)

  GetProcAddress(hLibrary, "SetupDiClassGuidsFromNameA");

 SetupDiGetClassDevsFunPtr = (SetupDiGetClassDevsFunType*)

  GetProcAddress(hLibrary, "SetupDiGetClassDevsA");

 SetupDiGetDeviceRegistryPropertyFunPtr = (SetupDiGetDeviceRegistryPropertyFunType*)

  GetProcAddress(hLibrary, "SetupDiGetDeviceRegistryPropertyA");

#endif

  SetupDiDestroyDeviceInfoListFunPtr = (SetupDiDestroyDeviceInfoListFunType*)

  GetProcAddress(hLibrary, "SetupDiDestroyDeviceInfoList");

 SetupDiEnumDeviceInfoFunPtr = (SetupDiEnumDeviceInfoFunType*)

  GetProcAddress(hLibrary, "SetupDiEnumDeviceInfo");

 //First need to convert the name "Ports" to a GUID using SetupDiClassGuidsFromName

 dwGuids = 0;

 SetupDiClassGuidsFromNameFunPtr(TEXT("Ports"), NULL, 0, &dwGuids);

 if(0 == dwGuids)

  return FALSE;

 //Allocate the needed memory

 pGuid = (GUID*)HeapAlloc(GetProcessHeap(),

  HEAP_GENERATE_EXCEPTIONS, dwGuids * sizeof(GUID));

 if(NULL == pGuid)

  return FALSE;

 //Call the function again

 if (FALSE == SetupDiClassGuidsFromNameFunPtr(TEXT("Ports"),

   pGuid, dwGuids, &dwGuids))

 {

  return FALSE;

 }/*if*/

 hDevInfoSet = SetupDiGetClassDevsFunPtr(pGuid, NULL, NULL,

  DIGCF_PRESENT /*| DIGCF_DEVICEINTERFACE*/);

 if (INVALID_HANDLE_VALUE == hDevInfoSet)

 {

  //Set the error to report

  _tprintf(TEXT("error SetupDiGetClassDevsFunPtr, %d"), GetLastError());

  return FALSE;

 }/*if */

 //bMoreItems = TRUE;

 devInfo.cbSize = sizeof(SP_DEVINFO_DATA);

 i = 0;

 jj = 0;

 do

 {

  HKEY hDeviceKey;

  BOOL isFound;

  isFound = FALSE;

  bMoreItems = SetupDiEnumDeviceInfoFunPtr(hDevInfoSet, i, &devInfo);

  if(FALSE == bMoreItems)

   break;   

  i++;

  hDeviceKey = SetupDiOpenDevRegKeyFunPtr(hDevInfoSet, &devInfo,

   DICS_FLAG_GLOBAL, 0, DIREG_DEV, KEY_QUERY_VALUE);

  if (INVALID_HANDLE_VALUE != hDeviceKey)

  {

   int nPort;

   size_t nLen;

   LPTSTR pszPortName;

   nPort = 0;

   pszPortName = NULL;

   {

    //First query for the size of the registry value

    DWORD dwType;

    DWORD dwDataSize;

    LONG err;

    DWORD dwAllocatedSize;

    DWORD dwReturnedSize;

    dwType = 0; dwDataSize = 0; 

    err = RegQueryValueEx(hDeviceKey, TEXT("PortName"), NULL,

     &dwType, NULL, &dwDataSize);

    if (ERROR_SUCCESS != err)

     continue;    

    //Ensure the value is a string

    if (dwType != REG_SZ)

     continue;

    //Allocate enough bytes for the return value

    dwAllocatedSize = dwDataSize + sizeof(TCHAR);

    /* +sizeof(TCHAR) is to allow us to NULL terminate

     the data if it is not null terminated in the registry

    */

    pszPortName = (LPTSTR)LocalAlloc(LMEM_FIXED, dwAllocatedSize); 

    if (pszPortName == NULL)

     continue;

    //Recall RegQueryValueEx to return the data

    pszPortName[0] = TEXT('\0');

    dwReturnedSize = dwAllocatedSize;

    err = RegQueryValueEx(hDeviceKey, TEXT("PortName"), NULL,

     &dwType, (LPBYTE)pszPortName, &dwReturnedSize);

    if (ERROR_SUCCESS != err)

    {

     LocalFree(pszPortName);

     pszPortName = NULL;

     continue;

    }

    //Handle the case where the data just returned is the same size as the allocated size. This could occur where the data

    //has been updated in the registry with a non null terminator between the two calls to ReqQueryValueEx above. Rather than

    //return a potentially non-null terminated block of data, just fail the method call

    if (dwReturnedSize >= dwAllocatedSize)

     continue;        

    //NULL terminate the data if it was not returned NULL terminated because it is not stored null terminated in the registry

    if (pszPortName[dwReturnedSize/sizeof(TCHAR) - 1] != _T('\0'))

     pszPortName[dwReturnedSize/sizeof(TCHAR)] = _T('\0');

   }/*local varable*/

   //If it looks like "COMX" then

   //add it to the array which will be returned

   nLen = _tcslen(pszPortName);

   if (3 < nLen)

   {

     if (0 == _tcsnicmp(pszPortName, TEXT("COM"), 3))

     {

     if(FALSE == isdigit(pszPortName[3]) )

      continue;

    //Work out the port number

     _tcsncpy(pPortName + jj*strMaxLen, pszPortName,

     _tcsnlen(pszPortName, strMaxLen));

    //_stprintf_s(&portName[jj][0], strMaxLen, TEXT("%s"), pszPortName);

     }

     else

     {

      continue;

     }/*if 0 == _tcsnicmp(pszPortName, TEXT("COM"), 3)*/

   }/*if 3 < nLen*/

   LocalFree(pszPortName);

   isFound = TRUE;  

   //Close the key now that we are finished with it

   RegCloseKey(hDeviceKey);

  }/*INVALID_HANDLE_VALUE != hDeviceKey*/

  if(FALSE == isFound)

   continue;

  //If the port was a serial port, then also try to get its friendly name

  {

   TCHAR szFriendlyName[1024];

   DWORD dwSize;

   DWORD dwType;

   szFriendlyName[0] = _T('\0');

   dwSize = sizeof(szFriendlyName);

   dwType = 0;

   if( (TRUE == SetupDiGetDeviceRegistryPropertyFunPtr(hDevInfoSet, &devInfo,

       SPDRP_DEVICEDESC, &dwType, (PBYTE)(szFriendlyName),

       dwSize, &dwSize) ) && (REG_SZ == dwType)

   )

   {

    _tcsncpy(pFriendName + jj*strMaxLen, &szFriendlyName[0],

     _tcsnlen(&szFriendlyName[0], strMaxLen));

   }

   else

   {

    _stprintf_s(pFriendName + jj*strMaxLen, strMaxLen, TEXT(""));

   }/*if SetupDiGetDeviceRegistryPropertyFunPtr */

  }/*local variable */

  jj++;

 }while(1);

 HeapFree(GetProcessHeap(), 0, pGuid);

 *pNumber = jj;

 if(0 <jj)

  ret = TRUE;

 return ret;

}/*EnumerateComPortSetupAPISetupDiClassGuidsFromNamePort*/

BOOL EnumerateComPortRegistry(UINT *pNumber, TCHAR *pPortName, int strMaxLen)

{

  //What will be the return value from this function (assume the worst)

 UINT jj;

 BOOL ret;

 HKEY hSERIALCOMM;

 ret = FALSE;

 if ( ERROR_SUCCESS == RegOpenKeyEx(HKEY_LOCAL_MACHINE,

  TEXT("HARDWARE\\DEVICEMAP\\SERIALCOMM"), 0, KEY_QUERY_VALUE, &hSERIALCOMM)

  )

 {

    //Get the max value name and max value lengths

  DWORD dwMaxValueNameLen;

  DWORD dwMaxValueLen;

  DWORD dwQueryInfo;

  dwQueryInfo = RegQueryInfoKey(hSERIALCOMM, NULL, NULL,

  NULL, NULL, NULL, NULL, NULL,

  &dwMaxValueNameLen, &dwMaxValueLen, NULL, NULL);

  if(ERROR_SUCCESS == dwQueryInfo)

  {

   DWORD dwMaxValueNameSizeInChars, dwMaxValueNameSizeInBytes,

    dwMaxValueDataSizeInChars, dwMaxValueDataSizeInBytes;

   DWORD *pValueName;

   DWORD *pValueData;

   dwMaxValueNameSizeInChars = dwMaxValueNameLen + 1; //Include space for the NULL terminator

   dwMaxValueNameSizeInBytes = dwMaxValueNameSizeInChars * sizeof(TCHAR);

   dwMaxValueDataSizeInChars = dwMaxValueLen/sizeof(TCHAR) + 1; //Include space for the NULL terminator

   dwMaxValueDataSizeInBytes = dwMaxValueDataSizeInChars * sizeof(TCHAR);

   //Allocate some space for the value name and value data      

   pValueName = (GUID*)HeapAlloc(GetProcessHeap(),

    HEAP_GENERATE_EXCEPTIONS| HEAP_ZERO_MEMORY, dwMaxValueNameSizeInBytes);

   pValueData = (GUID*)HeapAlloc(GetProcessHeap(),

    HEAP_GENERATE_EXCEPTIONS| HEAP_ZERO_MEMORY, dwMaxValueDataSizeInBytes);

   if(NULL != pValueName && NULL != pValueData)

   {

    //Enumerate all the values underneath HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM

    DWORD i;

    DWORD dwType;

    DWORD dwValueNameSize;

    DWORD dwDataSize;

    LONG nEnum;

    dwValueNameSize = dwMaxValueNameSizeInChars;

    dwDataSize = dwMaxValueDataSizeInBytes;

    i = 0; 

    nEnum = RegEnumValue(hSERIALCOMM, i,

     pValueName, &dwValueNameSize, NULL, &dwType,

     pValueData, &dwDataSize);

    jj = 0;

    while (ERROR_SUCCESS == nEnum)

    {

      //If the value is of the correct type, then add it to the array

     if (REG_SZ == dwType)

     {

      _stprintf_s(pPortName + jj*strMaxLen,

       strMaxLen, TEXT("%s"), pValueData);

      jj++;

     }/*if */

     //Prepare for the next time around

     dwValueNameSize = dwMaxValueNameSizeInChars;

     dwDataSize = dwMaxValueDataSizeInBytes;

     ZeroMemory(pValueName, dwMaxValueNameSizeInBytes);

     ZeroMemory(pValueData, dwMaxValueDataSizeInBytes);

     i++;

     nEnum = RegEnumValue(hSERIALCOMM, i, pValueName,

       &dwValueNameSize, NULL, &dwType, pValueData, &dwDataSize);

    }/*while*/

   }

   else

   {

    return FALSE;

   }/*if NULL != pValueName && NULL != pValueData*/

   HeapFree(GetProcessHeap(), 0, pValueName);

   HeapFree(GetProcessHeap(), 0, pValueData);

  }/*ERROR_SUCCESS == dwQueryInfo*/

  //Close the registry key now that we are finished with it

  RegCloseKey(hSERIALCOMM);

  if (dwQueryInfo != ERROR_SUCCESS)

    return FALSE;

 }/*ERROR_SUCCESS == RegOpenKeyEx*/

 *pNumber = jj;

 if(0 <jj)

  ret = TRUE;

 return ret;

}/*EnumerateComPortRegistry*/

#define TIMER_BEGIN(TIMER_LABEL) \

   { unsigned int tBegin##TIMER_LABEL, tEnd##TIMER_LABEL; \

   tBegin##TIMER_LABEL = GetTime();

#define TIMER_END(TIMER_LABEL)  \

   tEnd##TIMER_LABEL = GetTime();\

   fprintf(stderr, "%s cost time = %d ms\n", \

   #TIMER_LABEL, tEnd##TIMER_LABEL - tBegin##TIMER_LABEL); \

   }

unsigned int GetTime(void)

{

 /*winmm.lib*/

 return ( unsigned int)timeGetTime();

}/*GetTime*/

int main(int argc, TCHAR argv[])

{

 TCHAR portName[MAX_PORT_NUM][MAX_STR_LEN];

 TCHAR friendlyName[MAX_PORT_NUM][MAX_STR_LEN];

 UINT i;

 UINT n;

 char* nativeLocale;

 nativeLocale = _strdup( setlocale(LC_CTYPE,NULL) );

 for(i = 0; i< MAX_PORT_NUM; i++)

  ZeroMemory(&portName[i][0], MAX_STR_LEN);

 _tprintf(TEXT("\nCreateFile method : \n"));

TIMER_BEGIN(EnumerateComPortByCreateFile);

 EnumerateComPortByCreateFile(&n, &portName[0][0], MAX_STR_LEN);

TIMER_END(EnumerateComPortByCreateFile);

 _tprintf(TEXT("sought %d:\n"), n);

 for(i = 0; i< n; i++)

  _tprintf(TEXT("\t%s\n"), &portName[i][0]);

 for(i = 0; i< MAX_PORT_NUM; i++)

  ZeroMemory(&portName[0][0], MAX_STR_LEN);

 _tprintf(TEXT("\nQueryDosDevice method : "));

TIMER_BEGIN(EnumerateComPortQueryDosDevice);

 EnumerateComPortQueryDosDevice(&n, &portName[0][0], MAX_STR_LEN);

TIMER_END(EnumerateComPortQueryDosDevice);

 _tprintf(TEXT("sought %d:\n"), n);

 for(i = 0; i< n; i++)

  _tprintf("\t%s\n", &portName[i][0]);

 for(i = 0; i< MAX_PORT_NUM; i++)

  ZeroMemory(&portName[i][0], MAX_STR_LEN);

 _tprintf(TEXT("\nGetDefaultCommConfig method : \n"));

TIMER_BEGIN(EnumerateComPortByGetDefaultCommConfig);

 EnumerateComPortByGetDefaultCommConfig(&n, &portName[0][0], MAX_STR_LEN);

TIMER_END(EnumerateComPortByGetDefaultCommConfig);

 _tprintf(TEXT("sought %d:\n"), n);

 for(i = 0; i< n; i++)

  _tprintf(TEXT("\t%s\n"), &portName[i][0]);

 for(i = 0; i< MAX_PORT_NUM; i++){

  ZeroMemory(&portName[i][0], MAX_STR_LEN);

  ZeroMemory(&friendlyName[i][0], MAX_STR_LEN);

 }/*for i[i MAX_PORT_NUM]*/

 _tprintf(TEXT("\nSetupAPI GUID_DEVINTERFACE_COMPORT method : \n")); 

TIMER_BEGIN(EnumerateComPortSetupAPI_GUID_DEVINTERFACE_COMPORT);

 EnumerateComPortSetupAPI_GUID_DEVINTERFACE_COMPORT(&n, &portName[0][0],

  MAX_STR_LEN, &friendlyName[0][0]);

TIMER_END(EnumerateComPortSetupAPI_GUID_DEVINTERFACE_COMPORT);

 _tprintf(TEXT("sought %d:\n"), n);

 setlocale(LC_CTYPE, "" );

 for(i = 0; i< n; i++)

  _tprintf(TEXT("\t%s <%s> \n"), &portName[i][0],  &friendlyName[i][0]);

 setlocale(LC_CTYPE, nativeLocale);

 for(i = 0; i< MAX_PORT_NUM; i++){

  ZeroMemory(&portName[i][0], MAX_STR_LEN);

  ZeroMemory(&friendlyName[i][0], MAX_STR_LEN);

 }/*for i[i MAX_PORT_NUM]*/

 _tprintf(TEXT("\nSetupAPI SetupDiClassGuidsFromNamePort method : \n"));

TIMER_BEGIN(EnumerateComPortSetupAPISetupDiClassGuidsFromNamePort);

 EnumerateComPortSetupAPISetupDiClassGuidsFromNamePort(&n, &portName[0][0],

  MAX_STR_LEN, &friendlyName[0][0]);

TIMER_END(EnumerateComPortSetupAPISetupDiClassGuidsFromNamePort);

 _tprintf(TEXT("sought %d:\n"), n);

 setlocale(LC_CTYPE, "" );

 for(i = 0; i< n; i++)

  _tprintf(TEXT("\t%s <%s> \n"), &portName[i][0],  &friendlyName[i][0]);

 setlocale(LC_CTYPE, nativeLocale);

 for(i = 0; i< MAX_PORT_NUM; i++)

  ZeroMemory(&portName[i][0], MAX_STR_LEN);

 _tprintf(TEXT("\nRegistry method : \n"));

TIMER_BEGIN(EnumerateComPortRegistry);

 EnumerateComPortRegistry(&n, &portName[0][0], MAX_STR_LEN);

TIMER_END(EnumerateComPortRegistry);

 _tprintf(TEXT("sought %d:\n"), n);

 for(i = 0; i< n; i++)

  _tprintf(TEXT("\t%s\n"), &portName[i][0]);

 return 0;

}/*main*/

The output be :

CreateFile method :

EnumerateComPortByCreateFile cost time = 35 ms

sought 5:

        \\.\COM1

        \\.\COM4

        \\.\COM5

        \\.\COM98

        \\.\COM99

QueryDosDevice method : EnumerateComPortQueryDosDevice cost time = 7 ms

sought 5:

        COM5

        COM1

        COM98

        COM99

        COM4

GetDefaultCommConfig method :

EnumerateComPortByGetDefaultCommConfig cost time = 772 ms

sought 5:

        COM1

        COM4

        COM5

        COM98

        COM99

SetupAPI GUID_DEVINTERFACE_COMPORT method :

EnumerateComPortSetupAPI_GUID_DEVINTERFACE_COMPORT cost time = 12 ms

sought 2:

        COM1 <通訊連接埠>

        COM4 <USB Serial Port>

SetupAPI SetupDiClassGuidsFromNamePort method :

EnumerateComPortSetupAPISetupDiClassGuidsFromNamePort cost time = 10 ms

sought 5:

        COM99 <Bluetooth Serial Port>

        COM4 <USB Serial Port>

        COM1 <通訊連接埠>

        COM98 <Bluetooth Serial Port>

        COM5 <USB-SERIAL CH340>

Registry method :

EnumerateComPortRegistry cost time = 0 ms

sought 5:

        COM98

        COM99

        COM5

        COM1

        COM4

Note that: EnumerateComPortSetupAPI_GUID_DEVINTERFACE_COMPORT

would not list CH340 port, which is on an Arduino UNO board. (But the same function could list other CH340 port, if it is not on this Arduino). Besides,  this function could not list Bluetooth virtual com ports.

     

     If you would like to use my code, I suggest you use function

BOOL EnumerateComPortSetupAPISetupDiClassGuidsFromNamePort(UINT *pNumber,

  TCHAR *pPortName, int strMaxLen, TCHAR *pFriendName)

That is the best one which balances speed and detail; but this one are most complicated in implementation. Otherwise, if you want to implement a function which could list com ports as simple as possible, I recommend use theCreateFilemethod:
that is rudimentary, but sufficient.

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