🚀 go-pugleaf

Il Fri, 25 Jan 2008 14:26:01 +0100, "Anton" <acvoosten@zeelandnet.nl> ha scritto:

[snip]
>With a few of those existing virtual ports which are not really active, it 
>takes more then 10 seconds to open them and that's just the thing I want to 
>avoid.
>Maybe there's a timeout you can set or something else?
[snip]

Hi Anton

    ten seconds? Uhm... I never seen a such behaviour when opening a com port. 
For example, AFAIK, if the USB of a virtual COM port is unplugged, the port simply
disappears. However, I use the following code to detect if a comport exists and if it's
available. The fn returns true if the com exists and set the 2nd parameter to true
if it's busy.

bool IsComPortAvailable( int PortNumber, bool& InUse )
{
    AnsiString const ComName = AnsiString( "\\\\.\\COM" ) + PortNumber;

    HANDLE const hComm =
        CreateFile(
            ComName.c_str(),
            GENERIC_READ | GENERIC_WRITE,
            0,
            0,
            OPEN_EXISTING,
            0,
            0
        );

    if ( hComm == INVALID_HANDLE_VALUE ) {
        DWORD const dwError = GetLastError();
        if ( dwError == 5 )  // Port exists, but cannot be opened
            InUse = true;
        else if ( dwError == 2 )  // Port does not exist
            return false;
    }
    else {
        CloseHandle( hComm );
        InUse = false;
    }

    return true;
}

Regards

Giuliano