Missing INTERNET_STATUS_REQUEST_COMPLETE callback after calling Wininet’s FtpOpenFile() in asynchronous mode

Symptom:

To reproduce the issue:
1.       Put a zero byte file on a FTP site.

2.       Call InternetOpen() with flag INTERNET_FLAG_ASYNC

3.       FtpOpenFile() to download the file.

Wininet will send out a FTP request. After receiving the response, the registered callback procedure will receive an INTERNET_STATUS_REQUEST_COMPLETE event.

4.       Call FtpOpenFile() again.

This time Wininet will not send out any FTP request, nor raise the INTERNET_STATUS_REQUEST_COMPLETE event.

The application will then hang if it waits for the above event.

This issue happens only if in asynchronous mode. A zero byte file can always reproduce the issue.

Troubleshooting:

There is a Wininet asynchronous mode sample about how to download HTTP files: http://msdn.microsoft.com/en-us/library/cc185684(VS.85).aspx

Although it is HTTP not FTP, we can learn some ideas from that sample.

Solution:

After test and test, it was found that if we add flag INTERNET_FLAG_RELOAD when calling FtpOpenFile(), it began to work properly.

FtpOpenFile(hFtp_,path,GENERIC_READ,FTP_TRANSFER_TYPE_BINARY|INTERNET_FLAG_RELOAD,reinterpret_cast<DWORD_PTR>(this));

According to http://msdn.microsoft.com/en-us/library/aa383661(VS.85).aspx :

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