Asynch wininet - Threaded or not?

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Subject Author Date Asynch wininet - Threaded or not? Fred 02-01-2006  Re: Asynch wininet - Threaded or not? Scherbina Vladi... 02-01-2006  Re: Asynch wininet - Threaded or not? Scherbina Vladi... 02-02-2006  Re: Asynch wininet - Threaded or not? Fred 02-02-2006  Re: Asynch wininet - Threaded or not? Fred 02-02-2006  Re: Asynch wininet - Threaded or not? Fred 02-02-2006  Re: Asynch wininet - Threaded or not? Fred 02-02-2006  Re: Asynch wininet - Threaded or not? Scherbina Vladi... 02-02-2006  Re: Asynch wininet - Threaded or not? Fred 02-03-2006  Re: Asynch wininet - Threaded or not? Scherbina Vladi... 02-03-2006  Re: Asynch wininet - Threaded or not? Fred 02-03-2006

Posted by Fred on February 1, 2006, 9:51 am Please log in for more thread options Hi, If I use asynch Wininet is there any purpose in hiving of the Wininet calls into separate threads and the extra complication which ensues? As from what I can see the system starts a separate thread implicitly for the asynch calls anyway. The reason I ask is I imagine the thread switching might ensure that the UI remains responsive - plus there may be other issues you can enlighten me with. My application is "real-time" and will be applied to a Pocket PC/Smartphone as well as WinXP so I need the quickest/most efficient functionality possible. Also the UI response must be as fast as possible. The application basically "GET"s a website for info then issues occasional - through crucial "POST"s prompted by the user via the UI. Both the GETS and POSTS must be carried out as close to real-time as possible. TIA Posted by Scherbina Vladimir on February 1, 2006, 4:27 pm Please log in for more thread options Hello, Fred. show/hide quoted text > Hi, > If I use asynch Wininet is there any purpose in hiving of the Wininet > calls > into separate threads and the extra complication which ensues? As from > what > I can see the system starts a separate thread implicitly for the asynch > calls anyway. > The reason I ask is I imagine the thread switching might ensure that the > UI > remains responsive - plus there may be other issues you can enlighten me > with. > My application is "real-time" and will be applied to a Pocket > PC/Smartphone > as well as WinXP so I need the quickest/most efficient functionality > possible. > Also the UI response must be as fast as possible. > The application basically "GET"s a website for info then issues > occasional - > through crucial "POST"s prompted by the user via the UI. > Both the GETS and POSTS must be carried out as close to real-time as > possible. > TIA Even if you use wininet synchronously system might create additional threads and you cannot control this behavour. So putting async. calls into separate thread is useless. You may achieve the fastest result by creating the "worker" thread that waits on some object (for instance, event) and when GUI thread is going to make a GET or POST it sets the event and allows worker thread to accomplish the actual work using syncronous wininet calls. -- Vladimir Posted by Scherbina Vladimir on February 2, 2006, 12:33 am Please log in for more thread options show/hide quoted text > Hi, > I have built a related application which uses synchronous Wininet. However > I > have never worked out how to terminate a single thread if it hangs. The MS > workarounds to the wininet bug seem to terminate all active Wininet calls. Documentation states that if you have a thread that is reading or writing something to/from stream using HINTERNET handle you can close that handle on another thread using InternetCloseHandle. So if you have you "worker" sending POST or GET via HttpSendRequest closing HINTERNET handle that is used in HttpSendRequest will cancel sending request. -- Vladimir Posted by Fred on February 2, 2006, 6:31 am Please log in for more thread options show/hide quoted text > > Hi, > > I have built a related application which uses synchronous Wininet. However show/hide quoted text > > I > > have never worked out how to terminate a single thread if it hangs. The MS show/hide quoted text > > workarounds to the wininet bug seem to terminate all active Wininet calls. show/hide quoted text > Documentation states that if you have a thread that is reading or writing > something to/from stream using HINTERNET handle you can close that handle on show/hide quoted text > another thread using InternetCloseHandle. So if you have you "worker" > sending POST or GET via HttpSendRequest closing HINTERNET handle that is > used in HttpSendRequest will cancel sending request. I have read that the cancelling thread MS fix, http://support.microsoft.com/kb/224318/EN-US/ will cancell all threads currently accessing the Internet - although I can't find the original reference which details this. I have also come across this assertion: "The async mode is most suited to applications which must be single threaded and stay responsive to the end user and in extreme performance and memory sensitive situations" Although that was in a very old book :) Posted by Fred on February 2, 2006, 2:40 pm Please log in for more thread options show/hide quoted text > Fred, > Let's discuss what your old book says: > "The async mode is most suited to applications which must be single threaded show/hide quoted text > and stay responsive to the end user and in extreme performance and memory > sensitive situations" > This is technically true, but don't be misled by it! > If an application must be single threaded, then synchronous mode by > definition will prevent it from returning to the message loop until it is > done. However, there is no such application in practice. Who's stopping you show/hide quoted text > from using multiple threads? Nobody! Only your own lack of knowledge about > multithreaded programming, perhaps. Yes as far as synchronous/asynchronous Wininet and multithreading is concerned. I have written a pretty complicated prog with a thread pool and synchronous Wininet and it works - but I'm still not happy about cancelling threads when we have a timed-out block. show/hide quoted text > The rest of it is presumably talking about the expense of creating a thread. show/hide quoted text > It takes a little time and it allocates some memory (the largest part of > which is the stack). However, these are not really relevant issues for most show/hide quoted text > applications. You're not going to be downloading thousands of web pages at > once are you? What is the extra complexity involved in writing asynch wininet? MS's asyncdemo doesn't look too bad http://msdn.microsoft.com/library/en-us/wininet/wininet/calling_wininet_functions_asynchronously.asp Similar Threads Posted Re: Asynch wininet - Threaded or not? 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