WinHTTP and Connection: close

Question

Having a strange problem on Windows 2003 32-bit server and WinHTTP.

I have a C/C++ application that uses WinHTTP that was working fine for many years.  Today I encountered a strange situation while getting response from Apache/PHP application.  WinHttpReadData returns a timeout error while reading the response.  However, when executing the application under the debugger, I noticed, that, in fact, all data were read OK.  The problem is caused by TCP connection closure.  The situation is like this:

 

1. WinHTTP application POSTs request (some XML document).

2. PHP application responses OK with "Connection: close" and "Content-Length: 7508" headers.

3. WinHTTP reads all data successfully and I see TCP ACK that aknowledges all data in the MS Network Monitor.

4. This is where the problem starts.  Nobody wants to close TCP connection.  I can see various ACKs coming from WinHTTP and PHP until WinHTTP resets the connection and my application gets a timeout error.  If I call WinHttpReadData with the buffer length that exactly match the Content-Length value, I get all the data successfully.

5. So, should WinHTTP terminate TCP connection after receiving all data declared in "Content-Length" header? Or it is a bug on the server side, since it sent "Connection: close" header?

I tried various options on WinHTTP side, like enabling and disabling Keep-Alive, but it doesn't change anything.

 

Thank you in advance.

 

Answer 1

It seems to be a networking development issue rather than MSXML issue. You can try Windows development forum. Hope it helps.

---

Shuhai Shen - I love programming, travel and photographing. Welcome to my blog: http://leonax.net

Answer 2

Hi,

I have the same problem with WinHTTP. Did you solve it?

Thanks in advance.

Answer 3

I solved it by forcing the closer on my end, when I received the number of bytes provided in the Content-Length header.  Normally, I would execute WinHttpReadData() until I get an empty return from it.  However, this server (Apache) doesn't close the connection.  So, I was waiting on ReadData() for a long time.