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When I use WinHttp in a synchronisation model, sometimes the WinHttpSendRequest can not return.
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Thanks for reaching out!
WinHttpSetTimeouts controls only specific phases (DNS resolve, connect, send, and receive) and does not cover the entire HTTP/HTTPS lifecycle, such as SSL handshake or proxy auto-detection. If asynchronous mode isn't an option, kindly check the alternatives below:
1.Worker Thread+ Manual Timeout: Run the synchronous request in a separate thread and use a timer to call WinHttpCloseHandle( ) if it exceeds your custom timeout. This effectively simulates a global timeout.
2.Status Callback: Register a callback using WinHttpSetStatusCallBack() to log and identify which stage the request hangs on.
3.Disable Auto Proxy Detection (WPAD): Use WINHTTP_ACCESS_TYPE_NO_PROXY or a fixed proxy setting to avoid indefinite waits during proxy discovery.
4.Pre-resolve DNS and Rescue Connections: Avoid repeated DNS or TCP setups where possible to reduce hang risks.
References: WinHttpSetTimeouts function (winhttp.h) - Win32 apps | Microsoft Learn
https://learn.microsoft.com/en-us/windows/win32/api/winhttp/nf-winhttp-winhttpsendrequest
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thanks for your reply.
for "1.Worker Thread+ Manual Timeout: Run the synchronous request in a separate thread and use a timer to call WinHttpCloseHandle( ) if it exceeds your custom timeout. This effectively simulates a global timeout."
this solution is multiple thread safe? I mean "WinHttpCloseHandle" is called in different thread with "Run the synchronous request in a separate thread", for example: call "WinHttpCloseHandle" in main thread, the worker thread will throw any exception in some cases?
Thanks for reaching out!
Yes, it is thread-safe, closing from the main thread while the worker thread waits in WinHttpSendRequest( ) will safely cancel the operation and return an error without crashing.
"If a synchronous call is pending, another thread can call WinHttpCloseHandle to cancel the request. The synchronous call will then return with ERROR_WINHTTP_OPERATION_CANCELLED"
"WinHttpCloseHandle" in main thread, the worker thread will throw any exception in some cases?
Answer: Calling WinHttpCloseHandle from the main thread while the worker thread is running a synchronous WinHttpSendRequest is safe. The worker thread will simply exit the call, and the API will return the error ERROR_WINHTTP_OPERATION_CANCELLED. No exceptions or crashes occur in this scenario.
Reference: https://learn.microsoft.com/en-us/windows/win32/api/winhttp/nf-winhttp-winhttpclosehandle
Let me know if you need any further help with this. I will be happy to assist.
If you find this helpful, Kindly mark the provided solution as "Accept Answer", so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.
"Hope you're doing well. We're following up on the thread. Please let us know whether the issue persists or has been resolved. If the issue has been resolved, kindly mark the response as "answered". so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.
We'll close this thread by 10th November, so we are hoping for your reply before that".
thanks very much
Thank you for your response. We will now proceed with closing the thread as per your confirmation. If you encounter any further issues, please feel free to raise a new thread.
WinHttpSetTimeouts already had been called in right way, but the issue still persist.
Does the WinHttpSetTimeouts can control all the http/https life timeout?
Is there any other solution except asynchronous mode?
Thanks for reaching out!
WinHttpSendRequest may hang in synchronous mode if timeouts aren't applied correctly. Please ensure WinHttpSetTimeouts is called right after WinHttpOpen() and before WinHttpSendRequest(). If issue still persist, consider using asynchronous mode or adding a status callback (WinHttpSetStatusCallBack) to identify where it stalls.
WinHttpSetTimeouts function (winhttp.h) - Win32 apps | Microsoft Learn
Let me know if you need any further help with this. I will be happy to assist.
If you find this helpful, Kindly mark the provided solution as "Accept Answer", so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.