FILE_NOT_FOUND when trying to open COM port C++ - c++

Question

I am trying to open a com port for reading and writing using C++ but I can't seem to pass the first stage of actually opening it. I get an INVALID_HANDLE_VALUE on the handle
with GetLastError FILE_NOT_FOUND. I have searched around the web for a couple of days I'm fresh out of ideas. I have searched through all the questions regarding COM on this website too.
I have scanned through the existing ports (or so I believe) to get the name of the port right.
I also tried combinations of _T("COM1") with the slashes, without the slashes, with colon, without colon and without the _T
I'm using windows 7 on 64 bit machine.
this is the code i got
I'll be glad for any input on this
void SendToCom(char* data, int len)
{
DWORD cbNeeded = 0;
DWORD dwPorts = 0;
EnumPorts(NULL, 1, NULL, 0, &cbNeeded, &dwPorts);
//What will be the return value
BOOL bSuccess = FALSE;
LPCSTR COM1 ;
BYTE* pPorts = static_cast<BYTE*>(malloc(cbNeeded));
bSuccess = EnumPorts(NULL, 1, pPorts, cbNeeded, &cbNeeded, &dwPorts);
if (bSuccess){
PORT_INFO_1* pPortInfo = reinterpret_cast<PORT_INFO_1*>(pPorts);
for (DWORD i=0; i<dwPorts; i++)
{
//If it looks like "COMX" then
size_t nLen = _tcslen(pPortInfo->pName);
if (nLen > 3)
{
if ((_tcsnicmp(pPortInfo->pName, _T("COM"), 3) == 0) ){
COM1 =pPortInfo->pName;
//COM1 ="\\\\.\\COM1";
HANDLE m_hCommPort = CreateFile( COM1 ,
GENERIC_READ|GENERIC_WRITE, // access ( read and write)
0, // (share) 0:cannot share the COM port
NULL, // security (None)
OPEN_EXISTING, // creation : open_existing
FILE_FLAG_OVERLAPPED, // we want overlapped operation
NULL // no templates file for COM port...
);
if (m_hCommPort==INVALID_HANDLE_VALUE)
{
DWORD err = GetLastError();
if (err == ERROR_FILE_NOT_FOUND) {
MessageBox(hWnd,"ERROR_FILE_NOT_FOUND",NULL,MB_ABORTRETRYIGNORE);
}
else
if(err == ERROR_INVALID_NAME) {
MessageBox(hWnd,"ERROR_INVALID_NAME",NULL,MB_ABORTRETRYIGNORE);
}
else
{
MessageBox(hWnd,"unkown error",NULL,MB_ABORTRETRYIGNORE);
}
}
else{
WriteAndReadPort(m_hCommPort,data);
}
}
pPortInfo++;
}
}
}
}

Answer 1

The Solution is to use
The Problem is, if your port is Bigger then 9 then you have to use the Syntax
LPCWSTR szPortName = L"\\\\.\\COM11";.

Answer 2

If you are on Windows 10 - running all system updates might help !
I had the same issue that opening port "COM4" returned an error ERROR_FILE_NOT_FOUND. When running the program as "Administrator" it worked. Now after a updating to 1511 the program can open "COM4" even not running as "Administrator".

Answer 3

http://www.cplusplus.com/forum/windows/163855/
Use CreateFileA(...) instead of CreateFile(...)

Answer 4

ERROR_FILE_NOT_FOUND can be produced from CreateFile(L"\\\\.\\COM1", ...) and CreateFile(L"COM1:", ...) after using the Device Manager to change the assigned COM Port number. Disabling and re-enabling the device, or unplugging and reconnecting the USB adapter resolves the issue.
A useful test to confirm whether it is your program or the system is to send data to the port in command prompt. A successful test will show an empty line. A failed test will show an error message.
C:\drop>echo > \\.\COM1
The system cannot find the file specified.
C:\drop>echo > \\.\COM1
C:\drop>