Marius Bancila’s Blog

I’ve seen this question many times asked in forums. Unfortunatelly, not all the answers are ok. A a good wait to find the available COM ports is by using function GetDefaultCommConfig, that returns the default configuration for a specified communication device. Following code shows how to use it:

#include 
#include  

// this can be defined in a separate file
#ifdef _UNICODE
  #define tstring std::wstring
#else
  #define tstring std::string
#endif   

void DetectComPorts(std::vector< tstring >& ports, size_t upperLimit = 128)
{
  for(size_t i=1; i<=upperLimit; i++)
  {
	TCHAR strPort[32] = {0};
	_stprintf(strPort, _T("\\\\.\\COM%d"), i);   

	DWORD dwSize = 0;
	LPCOMMCONFIG lpCC = (LPCOMMCONFIG) new BYTE[1];
	BOOL ret = GetDefaultCommConfig(strPort, lpCC, &dwSize);
	delete [] lpCC;	   

	lpCC = (LPCOMMCONFIG) new BYTE[dwSize];
	ret = GetDefaultCommConfig(strPort, lpCC, &dwSize);
	delete [] lpCC;   

	if(ret) ports.push_back(strPort);
  }
}

Here is an example of how to use this function:

int _tmain(int argc, _TCHAR* argv[])
{
  std::vector< tstring > ports;
  DetectComPorts(ports);   

  for(std::vector< tstring >::const_iterator it = ports.begin(); it != ports.end(); ++it)
  {
	std::cout << *it << std::endl;
  }   

  return 0;
}