WinAPI打开串口失败

串口号为COM11，通过WinAPI始终无法打开串口，才发现原因如下：

http://www.advancedvirtualcomport.com/faq.html

How do I open a virtual serial port with a number higher than 9 from my application?
Windows automatically maps COM1-COM9 ports to the right device name. COM ports with higher numbers should be opened as \\.\COMxxx, where xxx is a port number.

Example for C/C++/C#: 
hPort = CreateFile("\\\\.\\COM15", ...); 

Example for VB: 
hPort = CreateFile("\\.\COM15", ...); 

Example for Delphi: 
hPort := CreateFile('\\.\COM15', ...);

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另发现：如果出现1~9 COM port打不开，可能会因为是之前打开后忘记关闭了，系统自动映射会有记录，再次打开时无法成功打开，需要关闭该COM口或者重启电脑（比较裸）。