PCAN_CHANNEL_AVAILABLE
PCAN_CHANNEL_UNAVAILABLE
PCAN_CHANNEL_OCCUPIED
PCAN_CHANNEL_PCANVIEW
These are likely #define'd symbols or an enumeration. You need to study the API. One of the API functions may return a channel status. Your code might read something like:
int status = your_api_get_status();
switch (status)
{
case PCAN_CHANNEL_AVAILABLE:
qDebug() << "available";
break;
case PCAN_CHANNEL_UNAVAILABLE:
qDebug() << "unavailable";
break;
case PCAN_CHANNEL_OCCUPIED:
qDebug() << "occupied";
break;
case PCAN_CHANNEL_PCANVIEW:
qDebug() << "pcanview";
break;
default:
break;
}